SQL server connection issue using Spring

SQL server connection issue using Spring - java

I found an issue connecting my web application using JDBC or Spring to a SQLServer database (not Express).
At some point of my code I call:
this.conn = DriverManager.getConnection(db_connect_string, db_userid, db_password);
and the application is running correctly but, it's waiting and doesn't proceed. The same happens with another web application with:
getJdbcTemplate().query(...)
If I take a look to the db using:
SELECT SPID, STATUS, PROGRAM_NAME, LOGINAME=RTRIM(LOGINAME), HOSTNAME, CMD
FROM MASTER.DBO.SYSPROCESSES
WHERE DB_NAME(DBID) = 'myDB' AND DBID != 0
I can see there is a connection opened but "AWAITING COMMAND". No exception is handled, it's just waiting for something.
The SQL Server Profiler for that connection (Audit login) returns:
-- network protocol: TCP/IP
set quoted_identifier on
set arithabort off
set numeric_roundabort off
set ansi_warnings on
set ansi_padding on
set ansi_nulls on
set concat_null_yields_null on
set cursor_close_on_commit off
set implicit_transactions off
set language us_english
set dateformat mdy
set datefirst 7
set transaction isolation level read committed
It works until some weeks ago. I think it should be something related to SQLServer configuration, but I'm quite sure I didn't change anything. We can exclude a firewall issue because the connection is correctly created. Anyone could help me, please?
thanks,Andrea

As suggested by Mark Rotteveel it's a Java 1.6.0_29 bug.

Related

Can't connect to MySQL Database (Java) [duplicate]

This question already has answers here:
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
(51 answers)
Closed 6 years ago.
I'm trying to connect to the local MySQL server but I keep getting an error.
Here is the code.
public class Connect {
public static void main(String[] args) {
Connection conn = null;
try {
String userName = "myUsername";
String password = "myPassword";
String url = "jdbc:mysql://localhost:3306/myDatabaseName";
Class.forName("com.mysql.jdbc.Driver").newInstance();
conn = DriverManager.getConnection(url, userName, password);
System.out.println("Database connection established");
} catch (Exception e) {
System.err.println("Cannot connect to database server");
System.err.println(e.getMessage());
e.printStackTrace();
} finally {
if (conn != null) {
try {
conn.close();
System.out.println("Database Connection Terminated");
} catch (Exception e) {}
}
}
}
}
and the errors :
Cannot connect to database server
Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2333)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2370)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2154)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at Connect.main(Connect.java:16)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
at java.net.Socket.<init>(Socket.java:375)
at java.net.Socket.<init>(Socket.java:218)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:257)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:294)
... 15 more
I've set the classpath, made sure my.cnf had the skip network option commented out.
java version is 1.2.0_26 (64 bit)
mysql 5.5.14
mysql connector 5.1.17
I made sure that the user had access to my database.

I have had the same problem in two of my programs. My error was this:
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
I spent several days to solve this problem. I have tested many approaches that have been mentioned in different web sites, but non of them worked. Finally I changed my code and found out what was the problem. I'll try to tell you about different approaches and sum them up here.
While I was seeking the internet to find the solution for this error, I figured out that there are many solutions that worked for at least one person, but others say that it doesn't work for them! why there are many approaches to this error?
It seems this error can occur generally when there is a problem in connecting to the server. Maybe the problem is because of the wrong query string or too many connections to the database.
So I suggest you to try all the solutions one by one and don't give up!
Here are the solutions that I found on the internet and for each of them, there is at least on person who his problem has been solved with that solution.
Tip: For the solutions that you need to change the MySQL settings, you can refer to the following files:
Linux: /etc/mysql/my.cnf or /etc/my.cnf (depending on the Linux distribution and MySQL package used)
Windows: C:\**ProgramData**\MySQL\MySQL Server 5.6\my.ini (Notice it's ProgramData, not Program Files)
Here are the solutions:
changing bind-address attribute:
Uncomment bind-address attribute or change it to one of the following IPs:
bind-address="127.0.0.1"
or
bind-address="0.0.0.0"
commenting out "skip-networking"
If there is a skip-networking line in your MySQL config file, make it comment by adding # sign at the beginning of that line.
change "wait_timeout" and "interactive_timeout"
Add these lines to the MySQL config file:
[wait_timeout][1] = *number*
interactive_timeout = *number*
connect_timeout = *number*
Make sure Java isn't translating 'localhost' to [:::1] instead of [127.0.0.1]
Since MySQL recognizes 127.0.0.1 (IPv4) but not :::1 (IPv6)
This could be avoided by using one of two approaches:
In the connection string use 127.0.0.1 instead of localhost to avoid localhost being translated to :::1
Run java with the option -Djava.net.preferIPv4Stack=true to force java to use IPv4 instead of IPv6. On Linux, this could also be achieved by running (or placing it inside /etc/profile:
export _JAVA_OPTIONS="-Djava.net.preferIPv4Stack=true"
check Operating System proxy settings, firewalls and anti-virus programs
Make sure the Firewall, or Anti-virus software isn't blocking MySQL service.
Stop iptables temporarily on linux. If iptables are misconfigured they may allow tcp packets to be sent to mysql port, but block tcp packets from coming back on the same connection.
# Redhat enterprise and CentOS
systemctl stop iptables.service
# Other linux distros
service iptables stop
Stop anti-virus software on Windows.
change connection string
Check your query string. your connection string should be some thing like this:
dbName = "my_database";
dbUserName = "root";
dbPassword = "";
String connectionString = "jdbc:mysql://localhost/" + dbName + "?user=" + dbUserName + "&password=" + dbPassword + "&useUnicode=true&characterEncoding=UTF-8";
Make sure you don't have spaces in your string. All the connection string should be continues without any space characters.
Try to replace "localhost" with the loopback address 127.0.0.1.
Also try to add port number to your connection string, like:
String connectionString = "jdbc:mysql://localhost:3306/my_database?user=root&password=Pass&useUnicode=true&characterEncoding=UTF-8";
Usually default port for MySQL is 3306.
Don't forget to change username and password to the username and password of your MySQL server.
update your JDK driver library file
test different JDK and JREs (like JDK 6 and 7)
don't change max_allowed_packet
"max_allowed_packet" is a variable in MySQL config file that indicates the maximum packet size, not the maximum number of packets. So it will not help to solve this error.
change tomcat security
change TOMCAT6_SECURITY=yes to TOMCAT6_SECURITY=no
use validationQuery property
use validationQuery="select now()" to make sure each query has responses
AutoReconnect
Add this code to your connection string:
&autoReconnect=true&failOverReadOnly=false&maxReconnects=10
Although non of these solutions worked for me, I suggest you to try them. Because there are some people who solved their problem with following these steps.
But what solved my problem?
My problem was that I had many SELECTs on database. Each time I was creating a connection and then closing it. Although I was closing the connection every time, but the system faced with many connections and gave me that error. What I did was that I defined my connection variable as a public (or private) variable for whole class and initialized it in the constructor. Then every time I just used that connection. It solved my problem and also increased my speed dramatically.
#Conclusion#
There is no simple and unique way to solve this problem. I suggest you to think about your own situation and choose above solutions. If you take this error at the beginning of the program and you are not able to connect to the database at all, you might have problem in your connection string. But If you take this error after several successful interaction to the database, the problem might be with number of connections and you may think about changing "wait_timeout" and other MySQL settings or rewrite your code how that reduce number of connections.

If you are using MAMP PRO, the easy fix, which I really wish I had realized before I started searching the internet for days trying to figure this out. Its really this simple...
You just have to click "Allow Network Access to MySQL" from the MAMP MySQL tab.
Really, thats it.
Oh, and you MIGHT have to still change your bind address to either 0.0.0.0 or 127.0.0.1 like outlined in the posts above, but clicking that box alone will probably solve your problems if you are a MAMP user.

Setting the bind-address to the server's network IP instead of the localhost default, and setting privileges on my user worked for me.
my.cnf:
bind-address = 192.168.123.456
MySql Console:
GRANT ALL PRIVILEGES ON dbname.* to username#'%' IDENTIFIED BY 'password';

In my case,
Change the remote machine mysql configuration at /etc/mysql/my.cnf: change
bind-address = 127.0.0.1
to
#bind-address = 127.0.0.1
On the remote machine, change mysql user permissions with
GRANT ALL PRIVILEGES ON *.* TO 'user'#'%' IDENTIFIED BY 'password';
IMPORTANT: restart mysql on the remote machine: sudo /etc/init.d/mysql restart

I've just faced the same problem.
It happened because the MySQL Daemon was binded to the IP of the machine, which is required to make connection with an user that has permission to connect #your_machine.
In this case, the user should have permission to connect USER_NAME#MACHINE_NAME_OR_IP
I wanted remote access to my machine so I changed in my.cnf from
bind-address = MY_IP_ADDRESS
To
bind-address = 0.0.0.0
Which will allow an user from localhost AND even outside (in my case) to connect to the instance.
Both below permissions will work if you bind the MySQL to 0.0.0.0:
USER_NAME#MACHINE_NAME_OR_IP
USER_NAME#localhost

In my case (I am a noob), I was testing Servlet that make database connection with MySQL and one of the Exception is the one mentioned above.
It made my head swing for some seconds but I came to realize that it was because I have not started my MySQL server in localhost.
After starting the server, the problem was fixed.
So, check whether MySQL server is running properly.

In case you are having problem with a set of Docker containers, then make sure that you do not only EXPOSE the port 3306, but as well map the port from outside the container -p 3306:3306. For docker-compose.yml:
version: '2'
services:
mdb:
image: mariadb:10.1
ports:
- "3306:3306"
…

In my case it was an idle timeout, that caused the connection to be dropped on the server. The connection was kept open, but not used for a long period of time. Then a client restart works, while I believe a reconnect will work as well.
A not bad solution is to have a daemon/service to ping the connection from time to time.

As the detailed answer above says, this error can be caused by many things.
I had this problem too. My setup was Mac OSX 10.8, using a Vagrant managed VirtualBox VM of Ubuntu 12.04, with MySQL 5.5.34.
I had correctly setup port forwarding in the Vagrant config file. I could telnet to the MySQL instance both from my Mac and from within the VM. So I knew the MySQL daemon was running and reachable. But when I tried to connect over JDBC, I got the "Communications link failure" error.
In my case, the problem was solved by editing the /etc/mysql/my.cnf file. Specifically, I commented out the "#bind-address=127.0.0.1" line.

The resolution provided by Soheil was successful in my case.
To clarify, the only change I needed to make was with MySQL's server configuration;
bind-address = **INSERT-IP-HERE**
I am using an external MySQL server for my application. It is a basic Debian 7.5 installation with MySQL Server 5.5 - default configuration.
IMPORTANT:
Always backup the original of any configuration files you may modify. Always take care when elevated as super user.
File
/etc/mysql/my.cnf
Line
bind-address = 192.168.0.103 #127.0.0.1
Restart your MySQL Server service:
/usr/sbin/service mysql restart
As you can see, I simply provided the network IP of the server and commented out the default entry. Please note that simply copy and paste my solution will not work for you, unless by some miracle our hosts share the same IP.
Thanks # Soheil

I know this is an old thread but I have tried numerous things and fixed my issue using the following means..
I'm developing a cross platform app on Windows but to be used on Linux and Windows servers.
A MySQL database called "jtm" installed on both systems. For some reason, in my code I had the database name as "JTM". On Windows it worked fine, in fact on several Windows systems it flew along.
On Ubuntu I got the error above time and time again. I tested it out with the correct case in the code "jtm" and it works a treat.
Linux is obviously a lot less forgiving about case sensitivity (rightly so), whereas Windows makes allowances.
I feel a bit daft now but check everything. The error message is not the best but it does seem fixable if you persevere and get things right.

I just restarted MySQL (following a tip from here: https://stackoverflow.com/a/14238800) and it solved the issue.
I had the same issue on MacOS (10.10.2) and MySql (5.6.21) installed via homebrew.
The confusing thing was that one of my apps connected to the database fine and the other was not.
After trying many things on the app that threw the exception com.mysql.jdbc.CommunicationsException as suggested by the accepted answer of this question to no avail, I was surprised that restarting MySQL worked.
The cause of my issue might have been the following as suggested in the answer in the aforementioned link:
Are you using connection pool ? If yes, then try to restart the
server. Probably few of the connections in your connection pool are in closed state.

It happens (in my case) when there is not enough memory for MySQL. A restart fixes it, but if that's the case consider a nachine with more memory, or limit the memory taken by jvms

Go to Windows services in the control panel and start the MySQL service. For me it worked. When I was doing a Java EE project I got this error" Communication link failure". I restarted my system and then it worked.
After that I again got the same error even after restarting my system. Then I tried to open the MySQL command line console and login with root, even then it gave me an error.
Finally when I started the MySQL service from Windows services, it worked.

Had the same.
Removing port helped in my case, so I left it as jdbc:mysql://localhost/

For me the solution was to change in the conf file of mysql server the parameter bind-address="127.0.0.1" or bind-address="x.x.x.x" to bind-address="0.0.0.0".
Thanks.

If you are using hibernate, this error can be caused for keeping open a Session object more time than wait_timeout
I've documented a case in here for those who are interested.

I found the solution
since MySQL need the Localhost in-order to work.
go to /etc/network/interfaces file and make sure you have the localhost configuration set there:
auto lo
iface lo inet loopback
NOW RESTART the Networking subsystem and the MySQL Services:
sudo /etc/init.d/networking restart
sudo /etc/init.d/mysql restart
Try it now

It is majorly because of weak connection between mysql client and remote mysql server.
In my case it is because of flaky VPN connection.

In phpstorm + vagrant autoReconnect driver option helped.

I was experiencing similar problem and the solution for my case was
changing bind-address = 0.0.0.0 from 127.0.0.1
changing url's localhost to localhost:3306
the thing i felt is we should never give up, i tried every options from this post and from other forums as well...happy it works #saurab

I faced this problem also.
As Soheil suggested,
I went to php.ini file at the path C:\windows\php.ini , then I revised port number in this file.
it is on the line mysqli.default_port =..........
So I changed it in my java app as it's in the php.ini file,now it works fine with me.

For Windows :-
Goto start menu write , "MySqlserver Instance Configuration Wizard" and reconfigure your mysql server instance.
Hope it will solve your problem.

After years having the same issue and no permanent solution this is whats solved it for the past 3 weeks (which is a record in terms of error free operation)
set global wait_timeout=3600;
set global interactive_timeout=230400;
Don't forget to make this permanent if it works for you.

If you are using local emulator, you have to use IP address 10.0.2.2 instead of localhost to access to your local MySQL server.

JDBC connection issue. Cannot connect while others can with same code [duplicate]

This question already has answers here:
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
(51 answers)
Closed 6 years ago.
I'm trying to connect to the local MySQL server but I keep getting an error.
Here is the code.
public class Connect {
public static void main(String[] args) {
Connection conn = null;
try {
String userName = "myUsername";
String password = "myPassword";
String url = "jdbc:mysql://localhost:3306/myDatabaseName";
Class.forName("com.mysql.jdbc.Driver").newInstance();
conn = DriverManager.getConnection(url, userName, password);
System.out.println("Database connection established");
} catch (Exception e) {
System.err.println("Cannot connect to database server");
System.err.println(e.getMessage());
e.printStackTrace();
} finally {
if (conn != null) {
try {
conn.close();
System.out.println("Database Connection Terminated");
} catch (Exception e) {}
}
}
}
}
and the errors :
Cannot connect to database server
Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2333)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2370)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2154)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at Connect.main(Connect.java:16)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
at java.net.Socket.<init>(Socket.java:375)
at java.net.Socket.<init>(Socket.java:218)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:257)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:294)
... 15 more
I've set the classpath, made sure my.cnf had the skip network option commented out.
java version is 1.2.0_26 (64 bit)
mysql 5.5.14
mysql connector 5.1.17
I made sure that the user had access to my database.

If you are using MAMP PRO, the easy fix, which I really wish I had realized before I started searching the internet for days trying to figure this out. Its really this simple...
You just have to click "Allow Network Access to MySQL" from the MAMP MySQL tab.
Really, thats it.
Oh, and you MIGHT have to still change your bind address to either 0.0.0.0 or 127.0.0.1 like outlined in the posts above, but clicking that box alone will probably solve your problems if you are a MAMP user.

Setting the bind-address to the server's network IP instead of the localhost default, and setting privileges on my user worked for me.
my.cnf:
bind-address = 192.168.123.456
MySql Console:
GRANT ALL PRIVILEGES ON dbname.* to username#'%' IDENTIFIED BY 'password';

In my case,
Change the remote machine mysql configuration at /etc/mysql/my.cnf: change
bind-address = 127.0.0.1
to
#bind-address = 127.0.0.1
On the remote machine, change mysql user permissions with
GRANT ALL PRIVILEGES ON *.* TO 'user'#'%' IDENTIFIED BY 'password';
IMPORTANT: restart mysql on the remote machine: sudo /etc/init.d/mysql restart

I've just faced the same problem.
It happened because the MySQL Daemon was binded to the IP of the machine, which is required to make connection with an user that has permission to connect #your_machine.
In this case, the user should have permission to connect USER_NAME#MACHINE_NAME_OR_IP
I wanted remote access to my machine so I changed in my.cnf from
bind-address = MY_IP_ADDRESS
To
bind-address = 0.0.0.0
Which will allow an user from localhost AND even outside (in my case) to connect to the instance.
Both below permissions will work if you bind the MySQL to 0.0.0.0:
USER_NAME#MACHINE_NAME_OR_IP
USER_NAME#localhost

In my case (I am a noob), I was testing Servlet that make database connection with MySQL and one of the Exception is the one mentioned above.
It made my head swing for some seconds but I came to realize that it was because I have not started my MySQL server in localhost.
After starting the server, the problem was fixed.
So, check whether MySQL server is running properly.

In case you are having problem with a set of Docker containers, then make sure that you do not only EXPOSE the port 3306, but as well map the port from outside the container -p 3306:3306. For docker-compose.yml:
version: '2'
services:
mdb:
image: mariadb:10.1
ports:
- "3306:3306"
…

In my case it was an idle timeout, that caused the connection to be dropped on the server. The connection was kept open, but not used for a long period of time. Then a client restart works, while I believe a reconnect will work as well.
A not bad solution is to have a daemon/service to ping the connection from time to time.

As the detailed answer above says, this error can be caused by many things.
I had this problem too. My setup was Mac OSX 10.8, using a Vagrant managed VirtualBox VM of Ubuntu 12.04, with MySQL 5.5.34.
I had correctly setup port forwarding in the Vagrant config file. I could telnet to the MySQL instance both from my Mac and from within the VM. So I knew the MySQL daemon was running and reachable. But when I tried to connect over JDBC, I got the "Communications link failure" error.
In my case, the problem was solved by editing the /etc/mysql/my.cnf file. Specifically, I commented out the "#bind-address=127.0.0.1" line.

The resolution provided by Soheil was successful in my case.
To clarify, the only change I needed to make was with MySQL's server configuration;
bind-address = **INSERT-IP-HERE**
I am using an external MySQL server for my application. It is a basic Debian 7.5 installation with MySQL Server 5.5 - default configuration.
IMPORTANT:
Always backup the original of any configuration files you may modify. Always take care when elevated as super user.
File
/etc/mysql/my.cnf
Line
bind-address = 192.168.0.103 #127.0.0.1
Restart your MySQL Server service:
/usr/sbin/service mysql restart
As you can see, I simply provided the network IP of the server and commented out the default entry. Please note that simply copy and paste my solution will not work for you, unless by some miracle our hosts share the same IP.
Thanks # Soheil

I know this is an old thread but I have tried numerous things and fixed my issue using the following means..
I'm developing a cross platform app on Windows but to be used on Linux and Windows servers.
A MySQL database called "jtm" installed on both systems. For some reason, in my code I had the database name as "JTM". On Windows it worked fine, in fact on several Windows systems it flew along.
On Ubuntu I got the error above time and time again. I tested it out with the correct case in the code "jtm" and it works a treat.
Linux is obviously a lot less forgiving about case sensitivity (rightly so), whereas Windows makes allowances.
I feel a bit daft now but check everything. The error message is not the best but it does seem fixable if you persevere and get things right.

I just restarted MySQL (following a tip from here: https://stackoverflow.com/a/14238800) and it solved the issue.
I had the same issue on MacOS (10.10.2) and MySql (5.6.21) installed via homebrew.
The confusing thing was that one of my apps connected to the database fine and the other was not.
After trying many things on the app that threw the exception com.mysql.jdbc.CommunicationsException as suggested by the accepted answer of this question to no avail, I was surprised that restarting MySQL worked.
The cause of my issue might have been the following as suggested in the answer in the aforementioned link:
Are you using connection pool ? If yes, then try to restart the
server. Probably few of the connections in your connection pool are in closed state.

It happens (in my case) when there is not enough memory for MySQL. A restart fixes it, but if that's the case consider a nachine with more memory, or limit the memory taken by jvms

Go to Windows services in the control panel and start the MySQL service. For me it worked. When I was doing a Java EE project I got this error" Communication link failure". I restarted my system and then it worked.
After that I again got the same error even after restarting my system. Then I tried to open the MySQL command line console and login with root, even then it gave me an error.
Finally when I started the MySQL service from Windows services, it worked.

Had the same.
Removing port helped in my case, so I left it as jdbc:mysql://localhost/

For me the solution was to change in the conf file of mysql server the parameter bind-address="127.0.0.1" or bind-address="x.x.x.x" to bind-address="0.0.0.0".
Thanks.

If you are using hibernate, this error can be caused for keeping open a Session object more time than wait_timeout
I've documented a case in here for those who are interested.

I found the solution
since MySQL need the Localhost in-order to work.
go to /etc/network/interfaces file and make sure you have the localhost configuration set there:
auto lo
iface lo inet loopback
NOW RESTART the Networking subsystem and the MySQL Services:
sudo /etc/init.d/networking restart
sudo /etc/init.d/mysql restart
Try it now

It is majorly because of weak connection between mysql client and remote mysql server.
In my case it is because of flaky VPN connection.

In phpstorm + vagrant autoReconnect driver option helped.

I was experiencing similar problem and the solution for my case was
changing bind-address = 0.0.0.0 from 127.0.0.1
changing url's localhost to localhost:3306
the thing i felt is we should never give up, i tried every options from this post and from other forums as well...happy it works #saurab

I faced this problem also.
As Soheil suggested,
I went to php.ini file at the path C:\windows\php.ini , then I revised port number in this file.
it is on the line mysqli.default_port =..........
So I changed it in my java app as it's in the php.ini file,now it works fine with me.

For Windows :-
Goto start menu write , "MySqlserver Instance Configuration Wizard" and reconfigure your mysql server instance.
Hope it will solve your problem.

After years having the same issue and no permanent solution this is whats solved it for the past 3 weeks (which is a record in terms of error free operation)
set global wait_timeout=3600;
set global interactive_timeout=230400;
Don't forget to make this permanent if it works for you.

If you are using local emulator, you have to use IP address 10.0.2.2 instead of localhost to access to your local MySQL server.

Trouble establishing a simple connection with JDBC to MySql, java.sql.SQLNonTransientConnectionException

I fail to establish a connection to a MySql database on an external server when I use the mysql-connector-java version 8.0.11+ (I was currently testing with 8.0.25). However I am able to create a connection when I use the older MySql connector mysql-connector-java version 5.1.49.
The version of the MySql Database is "8.0.25-15"
The code fails on the first line:
try (Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
{...}
Since I can connect though mysql-connector-java version 5.1.49, I first thought I could solve this problem by adding parameters to the DB_URL. I have experimented with a lot of parameters, but no luck:
useSSL=false
serverTimezone=GMT
useUnicode=true
characterEncoding=utf-8
passwordCharacterEncoding=utf-8
connectionCollation=utf8mb4_bin
autoReconnect=true
failOverReadOnly=false
maxReconnects=10
cacheServerConfiguration=false
The error I always receive is:
java.sql.SQLNonTransientConnectionException: Could not create connection to database server.
Caused by: java.lang.NullPointerException: Cannot invoke "String.toUpperCase(java.util.Locale)" because "javaEncoding" is null
at com.mysql.cj.CharsetMapping.getMysqlCharsetForJavaEncoding(CharsetMapping.java:552)
at com.mysql.cj.CharsetMapping.getCollationIndexForJavaEncoding(CharsetMapping.java:585)
at com.mysql.cj.protocol.a.NativeServerSession.configureCharacterSets(NativeServerSession.java:452)
at com.mysql.cj.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:1329)
at com.mysql.cj.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:866)
A month ago, I did not have this problem, so I suspect the cause is a change in the database (I am not tbe database Administrator).
When I debug, the error seems to be caused because the program requests the "character_set_system" variable from MySql, which is"utf8mb3" (instead "utf8" or "utf8mb4").
I suspect that changing the database variable "utf8mb3" to "utf8" might solve this problem? But I am not certain and I cannot simply change this value because the database is hosted by an external company. I have typed "Show Variables" and "Show Global Variables" in a MySql editor for your information:
A screenshot of the DB variables concerning language.
Alternatively I would like to tell java to ignore "character_set_system". It seems that Java first looks for "local.character_set_results", but this variable returns null despite that "character_set_results" is defined in the database.
I hope someone can help me with this problem.
Kind Regards
Steven

Tns connection issue in lotus java agent to jdbc connection via ojdbc14.jar [duplicate]

I have installed Oracle 11g Express Edition Release 2 in my windows 7 64 bit OS and tried to execute JDBC program, then I got the following error:
java.sql.SQLException: Listener refused the connection with the following error:
ORA-12505, TNS:listener does not currently know of SID given in connect descriptor
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:412)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:531)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:221)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:503)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.jlcindia.jdbc.JDBCUtil.geOracleConnection(JDBCUtil.java:28)
at Lab3O.main(Lab3O.java:15)
Caused by: oracle.net.ns.NetException: Listener refused the connection with the following error:
ORA-12505, TNS:listener does not currently know of SID given in connect descriptor
at oracle.net.ns.NSProtocol.connect(NSProtocol.java:385)
at oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:1042)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:301)
... 8 more

I fixed this issue by correcting my jdbc string.
For example, the correct jdbc string should be...
jdbc:oracle:thin:#myserver:1521/XE
But the jdbs string I was using is ...
jdbc:oracle:thin:#myserver:1521:XE
(Note: between 1521 and XE should be a /)
This bad jdbc string give me a ORA-12505 error too.

There are a few things that can cause this problem, but before you get started with JDBC, you need to be sure that you can connect to the database using SQL*Plus. If you're not familiar with SQL*Plus, it's a command-line tool for connecting to Oracle databases that has been a standard part of Oracle for a long time and it is included with Oracle XE.
When connecting to an Oracle database using JDBC, you don't connect to the database directly. Instead, you connect to a TNS listener, which then connects you to the database. The error ORA-12505 means that the listener was up and you could connect to it, but it couldn't connect you to the database because it doesn't know that that database is up. There are two reasons for this:
the database has not been started up,
the database has not registered with the listener, e.g. because the database was started before the listener. (When the database starts, it registers itself with a listener if it is already running. If the listener isn't running, the database doesn't register itself, and if the listener starts, it doesn't go looking for databases that might register with it.)
ORA-12505 means that the listener knows about that database, but the listener hasn't received a notification from the database that the database is up. (If you were trying to connect to the wrong database, using the wrong SID, you would get an ORA-12154 error "TNS: could not resolve the connect identifier specified".)
What Oracle services are running in the Services snap-in? (Open this from Control Panel > Administrative Tools > Services, or just Start > Run > services.msc.) You need the services OracleServiceXE and OracleXETNSListener to be running.
If the services have both been started, can you connect to the database in SQL*Plus using any of the following at a command prompt? (I'm assuming you're running these on the machine you've installed Oracle XE on.)
sqlplus system/system-password#XE
sqlplus system/system-password
sqlplus / as sysdba
(Replace system-password with the password you set for the SYS and SYSTEM users during the Oracle XE installation.)
The first of these three connect via the TNS listener, but the second two connect directly to the database without going via the listener, and only work if you're on the same machine as the database. If the first one fails but the other two succeed, then JDBC connections will also fail. If so, connect to the database using either of the other two and run ALTER SYSTEM REGISTER. Then exit from SQL*Plus and try the first form again.
If the third one fails but the second one works, add your user account to the ora_dba group. Do this in Control Panel > Computer Management > Local Users and Groups.
Once you can get connections of the form
sqlplus system/system-password#XE
to work, you ought to be able to connect to Oracle XE via JDBC. (Incidentally, you haven't shown us the JDBC code you're using to connect to the database, but I would suspect that it is quite probably correct; there would be various other errors if parts of the connection string were wrong.)

I too got the same error but when tried all the three of them failed.
If the above three fails.Try LSNRCTL status if you find the service (XE in my case)missing try this
sqlplus /nolog
conn system
alter system register;
exit
lsnrctl status
Now you can see the service
Even if don't see try this one out
sqlplus /nolog
conn system
alter system set local_listener = '(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521))' scope = both;
alter system register;
exit
lsnrctl status
This should probably work ...

When your getting this error "ORA-12505, TNS:listener does not currently know of SID given in connect descriptor"
Solution: Open Services, and start OracleServiceXE, after that try to connect...

If you have a working connection in Oracle SQL Developer, use the information on the connection menu to build your url, as described in the following image:
In the above example, the url would be : jdbc:oracle:thin:#ORADEV.myserver.com:1521/myservice
Note that if your are using a SID, then there is a colon (":") instead of a slash ("/") after the host name.

I found some reasons for this exception.they are
1)The name of the database XE by default.so the url will be"jdbc:oracle:thin:#localhost:1521:XE".
2)Make sure that OracleServiceXE,OracleXETNSListener is running.it will be in Control Panel\All Control Panel Items\Administrative Tools\Services

I solved this issue by correcting my JDBC code.
the correct JDBC string should be...
conection = DriverManager.getConnection
("jdbc:oracle:thin:#localhost:1521:xe","system","ishantyagi");
But the JDBC string I was using was ...
conection = DriverManager.getConnection
("jdbc:oracle:thin:#localhost:1521:orcl","system","ishantyagi");
So, the mistake of specifying orcl instead of xe showed this error as the SID name was wrong.

My issue is resolved when I use the below code:
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection conn=DriverManager.getConnection("jdbc:oracle:thin:#IPAddress:1521/servicename","userName","Password");

Faced similar error, any of the above solutions didn't help.
There was a problem in the listner.ora file. By mistake I had added SID out of the SID_LIST see below(section between the stars *).
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = C:\oraclexe\app\oracle\product\11.2.0\server)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = CLRExtProc)
(ORACLE_HOME = C:\oraclexe\app\oracle\product\11.2.0\server)
(PROGRAM = extproc)
)
)
*(SID_DESC =
(SID_NAME = XE)
(ORACLE_HOME = C:\oraclexe\app\oracle\product\11.2.0\server)
)*
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))
)
)
DEFAULT_SERVICE_LISTENER = (XE)
Corrected this error as below:
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = XE)
(ORACLE_HOME = C:\oraclexe\app\oracle\product\11.2.0\server)
)
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = C:\oraclexe\app\oracle\product\11.2.0\server)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = CLRExtProc)
(ORACLE_HOME = C:\oraclexe\app\oracle\product\11.2.0\server)
(PROGRAM = extproc)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))
)
)
DEFAULT_SERVICE_LISTENER = (XE)
Stopped and the database
Stopped the listeners OracleServiceXE and OracleXETNSListener manually as it did not stop automatically by going to Control Panel\All Control Panel Items\Administrative Tools\Services. Restarted the database and it worked like a charm.

Oracle:
Thin-style Service Name Syntax
Thin-style service names are supported only by the JDBC Thin driver. The syntax is:
#//host_name:port_number/service_name
http://docs.oracle.com/cd/B28359_01/java.111/b31224/urls.htm#BEIDHCBA

i initially came here with the same problem. I had jus installed Oracle 12c on Windows 8 (64-bit),but i have since resolved it by 'TNSPING xe' on the command line... If the connection isn't established or name not found,try the database name,in my case it was 'orcl'... 'TNSPING orcl' again and if it pings successfully then u need to change the SID to 'orcl' in this case (or whatever database name u used)...

One possibility that I haven't seen widely discussed is that there may be a problem resolving the hostname on the host machine itself. If there is no entry for $(hostname) in /etc/hosts, the Oracle listener gets confused and wont come up.
That turned out to be my problem, and adding the hostname and ip address in /etc/hosts resolved the problem.

I have faced the same issue and solved by restart the OracleServiceXE service. Goto Services.msc and then verify the 'OracleServiceXE' service is UP and running

I fixed this issue by changing "SID" to "SERVICE_NAME" in my TNSNAMES.ora file.
Please see if your DB asks for SID or SERVICE_NAME.
Cheers

Connection con=DriverManager.getConnection("jdbc:oracle:thin:#localhost:1521:xe","scott","tiger");
Error I got:
java.sql.SQLException: Listener refused the connection with the following error:
ORA-12505, TNS:listener does not currently know of SID given in connect descriptor
The Connection descriptor used by the client was:
localhost:1521:xe
How I solved it:
Connection con=DriverManager.getConnection("jdbc:oracle:thin:localhost:1521:xe","scott","tiger");
(Remove #)
Don't know why, but its working now...

I too faced the same issue. I had installed Oracle Express edition 10g in Windows XP OS using VMware and it was working fine. Since it was very awkward typing SQL queries in the SQL utility provided by 10g and since I was used to working with SQL developer, I installed 32 bit SQL developer in XP and tried connecting to my DB SID "XE". But the connection failed with error-ORA-12505 TNS listener doesn't currently know of SID given in connect descriptor. I was at sea as to how this problem occurred since it was working fine with the SQL utility and I had also created few Informatica mappings using the same. I did browse a lot on this stuff hither thither and applied the suggestions offered to me after pinging the status of "lsnrctl" on public forums but to no avail. However, this morning I tried creating a new connection again, and Voila, it worked with no issues. I am guessing after reading in few posts that sometimes listener listens before the DB connects or something(pardon me for my crude reference as I am a newbie here) but I suggest to just restart the machine and check again.

I had the same problem so to resolve this problem I first reconfigure my listener using netca after that I deleted my old database which was ORCL by using dbca and then i created the new database again using dbca

Please check both OracleServiceXE and OracleXETNSListener having the status started when you navigate through start->run->services.msc.
For my case only OracleXETNSListener was started but OracleServiceXE was not started, when I started by right clicking -> start and checked the connection its working for me

If you use Oracle Express Edition, you should have this url
jdbc:oracle:thin:#localhost:1521:xe or jdbc:oracle:thin:#localhost:1521/XE
I had similar problem with liquibase config plugin in pom.xml. And I changed my configuration:
`<configuration>
<driver>oracle.jdbc.OracleDriver</driver>
<url>jdbc:oracle:thin:#localhost:1521:xe</url>
<defaultSchemaName></defaultSchemaName>
<username>****</username>
<password>****</password>
</configuration>`

Check by doing tnsping and instance name in host machine. It will give u the tns decription and all most of the time host name is different which is not matching.
I resolve my issue likewise
In Unix machine
$ tnsping (Enter)
It gives me full tns description where I found that host name is different.. :)

I had similar problem in SQL Workbench.
URL:
jdbc:oracle:thin:#111.111.111.111:1111:xe
doesn't work.
URL:
jdbc:oracle:thin:#111.111.111.111:1111:asdb
works.
This help me in my concrete situation. I afraid, that could exists many other reasons with different solutions.

I got this error ORA-12505, TNS:listener does not currently know of SID given in connect descriptor when I tried to connect to oracle DB using SQL developer.
The JDBC string used was jdbc:oracle:thin:#myserver:1521/XE, obviously the correct one and the two mandatory oracle services OracleServiceXE, OracleXETNSListener were up and running.
The way I solved this issue (In Windows 10)
1. Open run command.
2. Type services.msc
3. Find services with name OracleServiceXE and OracleXETNSListener in the list.
4. Restart OracleServiceXE service first. After completing the restart try restarting OracleXETNSListener service.

Had a similar issue. The issue started occurring suddenly - we are having load balanced database connection URL, but in jdbc connections I was pointing to a single db directly.
Changed to load balanced db url and it worked.

In my case not was working out, finally i restarted my oracle and TNS listener and everything worked. Was struggling for 2 days.

Apart from running services(OracleServiceXE,OracleXETNSListener) on there is a chance your Anti-virus software/firewall may still block them. Just make sure they are not blocked.

I just fixed it by restarting / starting oracleService in services

My oracle stopped working and I was getting this error. I restarted my machine and also tried above solutions. Ultimately, I opened component services and restarted the oracle services and it all started working. Hope this helps someone.

I was just creating the database link incorrectly.
Simple fix for me was to simply change 'SID' to SERVICE_NAME
CREATE DATABASE LINK my_db_link
CONNECT TO myUser IDENTIFIED BY myPassword
USING
'
(
DESCRIPTION=
(
ADDRESS=
(PROTOCOL=TCP)
(HOST=host-name-heren)
(PORT=1521)
)
(CONNECT_DATA=(SID=theNameOfTheDatabase))
)';
Changing
SID=theNameOfTheDatabase
to
SERVICE_NAME=theNameOfTheDatabase
resolved my issue.

I encounter this problem because I did kill task to "Oracle" task in the Task Manager.
To fix it you need to open the cmd -> type: services.msc -> the window with all services will open -> find service "OracleServiceXE" -> right click: start.

#Luke Woodward's answer helped to identify my XE wasn't connecting.
I had an issue when connecting to a VPN. And I am using a fresh local Oracle 21c on Windows 11.
The files listener.ora and tnsnames.ora were using my PC name "ERIK-PC" like this:
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = ERIK-PC)(PORT = 1521))
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
)
)
I just needed to change ERIK-PC to localhost.
More information in this thread.
By the way, I am using Oracle 21c, and since 18c, the *.ora files are under installationfolder\homes\OraDB21Home1\network\admin\*.ora
Save your changes and restart the listener using a privileged windows shell:
lsnrctl stop
lsnrctl start

Java PostgreSQL connection over VPN

I have a Java application that needs to connect to a remote PostgreSQL database over a VPN. Here is the relevant code:
Class.forName("org.postgresql.Driver");
Connection con = null;
con = DriverManager.getConnection("jdbc:postgresql://" + sqlHost + ":" + sqlPort + "/mydb", username, password);
This throws the error
org.postgresql.util.PSQLException: FATAL: pg_hba.conf rejects connection for host "172.16.7.5", user "xxxxx", database "xxxxx", SSL off
The Host IP address in sqlHost is actually 192.168.12.55, but if you notice the error message says that it is connecting to host 172.16.7.5 (which is the IP address assigned by the VPN).
I am able to connect to this PostgreSQL database using the exact same connection parameters on the exact same VPN using PGAdmin and using Python's psocopg2 module. Here is the equivalent Python code:
conn = psycopg2.connect("dbname=mydb user="+username+" password="+password+" host="+sqlHost+" port="+sqlPort)
Why in the world is only Java having problems with this? Since the connection works over PGAdmin and Python, I assume there is some setting in Java that I am using incorrectly, but I can't find anything.
EDIT: After reading into PostgreSQL docs a little more, I found that the issue with it listing the wrong hostname is not part of the issue but rather just the way PostgreSQL sees my computer over the VPN. Problem is still not solved, however.

Okay, I fixed this myself. The problem had nothing to do with the VPN but rather with the fact that Java by default does not try any sort of SSL connection by default whereas PGAdmin and psycopg2 do.
The solution was to add the following parameters to my connection url:
ssl=true&sslfactory=org.postgresql.ssl.NonValidatingFactory

I'm not sure if this might be the problem, but I've experienced similar problems in the past trying to connect to a database with VPN turned on.
Try running your application with this JVM argument passed at application launch time:
-Djava.net.preferIPv4Stack=true
See also this answer for a more permanent solution.

We Keep Coding

Java is a programming language and computing platform first released by Sun Microsystems in 1995.