This question already has answers here:
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
(51 answers)
Closed 6 years ago.
I Have developed an application to capture data, retrieve information,delete and also update info. The application is developed in java swing and hibernate and uses MySQL version 5.5 as a database. I tested it on my local server or local host and its working fine. So now i took it a step further trying to access the database on the remote server. Please note that also the MySQL version i use on my local server is the same as the MySQL in the remote server.
I get the following error:
Internal Exception: 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.
Error Code: 0
The problem is that your MySqlConnector/Driver can't establish a Connection to the remote server.
Check your jdbc URL and also the check if the wrong ports are used.
Maybe the Mysql DB is not reachable from outside, than you can use a port forwarding with ssh, for example :
port forwarding:
ssh -L3306:127.0.0.1:3306 user#remoteServer
than change your jdbc url to:
jdbc:mysql://localhost:3306/database
Explanation:
-L port:host:hostport
Specifies that the given port on the local (client) host is to be
forwarded to the given host and port on the remote side.
...
Whenever a
connection is made to this port, the connection is forwarded over
the secure channel, and a connection is made to host port
hostport from the remote machine.
Source: http://www.openbsd.org/cgi-bin/man.cgi?query=ssh&sektion=1
That means you request with your MySQL JDBC Driver(jdbc url) on the local 3306 port
will be forwarded to the remote server on his local 3306 port,
where the Mysql Database is listing.
Related
Could you please guide me How can I connect my local SQL developer to MY SQL Server running on Docker container in EC2. But I havent installed mysql in my ec2 host.
I have tried with public dns and port 3306 but getting below error
An error occurred while establishing the connection:
`Long Message:
Communications link failure
The last packet successfully received from the server was 353 milliseconds ago. The last packet sent successfully to the server was 339 milliseconds ago.
Details:
Type: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException
SQL State: 08S01`
follow the guide in this official AWS documentation
https://aws.amazon.com/premiumsupport/knowledge-center/connect-http-https-ec2/
Use port 3306 however, this is a guide for webservers
This question already has answers here:
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
(51 answers)
Closed 3 years ago.
I was trying to access my java web app , which i have containerised with docker containers and i also have containerised my mysql database in a different container , both container are running on the default docker network , and i also tried to ping those containers from each other and i got positive results from it , but when i try to access it on my localhost (as i have mapped the ports of the tomcat server to the host ) machine it shows
Error
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 have read a little bit about this error , its related to some sort of connectivity issue with database but through pingcommand , i checked the connection.
What could be the reason of this error?
1) If it is bound to 127.0.0.1 and you can't connect using "localhost", make sure it's not resolving to the IPv6 localhost address instead of IPv4. (or just use the IP address)
2) Check the port that MySQL is listening on (Default 3306).
3) Make sure you're using the right JDBC connector for your JDK.
Check this below code in your application.yml or application.properties
spring.datasource.url=jdbc:mysql://localhost:3306/<<DB_NAME>>
spring.datasource.username=root (In my case)
I had a problem here, is it possible that JDBC connecting to the amazon MySQL server remotely? I searching on the Internet for solution but ended up receiving the error
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 am using jsch.jar to connect the remote server, then call up JDBC connector trying to connect MySQL DB, I had successfully connected to the remote server yet I cannot connect MySQL DB on amazon, here is my code
testPutty t = new testPutty();
t.connect("admin", "", "xx:xx:xx:xx", "openSSHPrivateKey", 22);
t.connect();
System.out.println("connected");
Class.forName("com.mysql.jdbc.Driver");
DriverManager.getConnection("jdbc:mysql://staging.ppyhcsxnlkji.ap-southwest-1.rds.amazonaws.com:3306/staging","superuser","password");
System.out.println("hello world");
t.close();
First set up the tunnel with SSH. You haven't shown what testPutty is so I'll assume it's a thin Java wrapper around a command line invocation of Putty. The command line option for setting up a tunnel is
-L[localport]:[host]:[remoteport]
For your example this would be
-L3306:staging.ppyhcsxnlkji.ap-southwest-1.rds.amazonaws.com:3306
This sets up a tunnel that forwards connections to local port 3306 to port 3306 on the given host (staging...amazonaws.com) on port 3306, routed through the host that is the target of the SSH command (in your sample xx:xx:xx:xx).
Then, your connection string needs to use localhost instead of the actual remote:
jdbc:mysql://localhost:3306/staging
If 3306 on your local host is not available because you are also running a local copy of MySQL, just choose a different unused port.
I am trying to test the connection from NetBeans IDE8.0 with New Connection Wizard to the Cpanel MySql Database .
I already added my machine ip address in the Remote MySql option of Cpanel but still i am not able to connect with database.
I am getting below error message
Cannot establish a connection to jdbc:mysql:// someIP:3306/hariom?zeroDateTimeBehavior=convertToNull using com.mysql.jdbc.Driver (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.)
If your server has ConfigServerFirewall installed you need to open the port there as well event though you turned on remote mysql on your cPanel. If you do not own the server you need to contact the host for this.
I get a communication link failure while application tries to establish a connection with DB.
[#|2010-04-08T20:09:57.825+0300|SEVERE|glassfish3.0|javax.enterprise.system.std.com.sun.enterprise.v3.services.impl|_ThreadID=24;_ThreadName=Thread-1;|Cannot connect to database 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.|#]
Precisely at this string:
Statement s = conn.createStatement();
where conn is defined as follows:
private static java.sql.Connection conn;
For this app I have set a connection pool with default parameters and currently it (app) uses both JPA and direct JDBC queries. Recreation of connection pool gave nothing, connection pool ping gave next message:
Ping Connection Pool for pool is Failed. Ping failed Exce
ption - Connection could not be allocated because: Communications lin
k failure%%%EOL%%%%%%EOL%%%The last packet sent successfully to the s
erver was 0 milliseconds ago. The driver has not received any packets
from the server. Please check the server.log for more details.%%%EOL
%%%Ping failed Exception - Connection could not be allocated because:
Communications link failure
and flushing the connection pool gave:
com.sun.enterprise.admin.cli.CommandException: remote failure: Failed to flush connection pool ...
However I can connect to the database from a terminal. Besides I have the same app working on my local machine with identical connection pool settings.
Any one has an idea on whats going on or how to solve the trouble?
Such problem could be if you have mysql server & glassfish server on the same host, and in mysql configuration you have option bind to some public address (for example 192.168.0.1 of eth0 interface) that normally successfully working with simple jdbc/jpa using user#localhost, but they don`t in a case of glassfish JTA, instead to bind to some of local address you getting link failure. As rule you could not bind to any local (localhost/127.0.0.1) addresses of such mysql host if public address presented.
Example:
my.cnf
bind-address = 127.0.0.1
bind-address = 192.168.0.1
127.0.0.1 - assign to lo interface
192.168.0.1 - assign to eth0 interface
It is glassfish-mysql bug.
Currently in order to use JTA, you should not bind mysql to such address. (remove "bind-address=192.168.0.1" from my.cnf). Or use user#192.168.0.1 what is less secure.
Besides I have the same app working on my local machine with identical connection pool settings.
Are you connecting to the same database? If yes, maybe check that you're using the same JDBC driver.
In my case I set :
URL : jdbc:mysql://10.81.35.66:3306/testDB
and
url : jdbc:mysql://10.81.31.76:3306/vectordb
both When setting values while creating connection pool in additional property part
on glass fish admin console .