i tried this code:
http://programming-guides.com/java/tcp-client-server-chat
(full example)
and it's working but when i switch the "host" int the client side to an external IP (insted of localhost) it give me this error:
"Cannot get IO for connection to.."
i treid to switch the port but it didnt work..
Is the server running on that remote machine? Is the port open in the firewall?
Try to netcat to the remote host. If you get an connection the example maybe wrong. If not, you cannot connect to that host: host not exists, not listen on that port, port is filtered, etc, etc.
Related
I'm trying to connect to server socket in java using my router's public ip,
first, I tried by simply configuring server socket to localhost, like this,
server = new ServerSocket(5000);
It is working on localhost but not working on trying internal ip 192.168.1.6
then, I tried configuring server socket to the internal Ip (saw this solution), code is as follows,
int backlog = 5;
server = new ServerSocket(5000, backlog, InetAddress.getByName("192.168.1.6"));
and it is working as my devices are connected to same network, I can connect to this Ip 192.168.1.6 from a device with Ip 192.168.1.5 on the same network but when I use public ip of my router from client side, connection is getting timed out, I've done port forwarding,
What am I doing wrong here? any help is appreciated, thanks in advance.
EDIT :
I came to about NAT-loopback (saw this solution) as I was trying to connect using public ip while being on same network so I tried different network but still it is not connecting, connection is getting timed out.
Firstly replace your port number by 8080, which is the default port for HTTP when you are not root. Then you have to open the port 8080 on your router to allow the client to connect.
Your server must be connected to the Internet and have a public IP address. Then the client can connect to this public IP address.
I'm working on a project using Java RMI and with a client-server implementation.
On the server side, this is how I initialize my server:
final String url = "localhost";
final int port = 8090;
LocateRegistry.createRegistry(port);
IServerGame serverGame = new ServerGame();
Naming.rebind("//"+url+":"+port+"/undercover", serverGame);
System.out.println("Server running at //" + url + ":" + port + "/undercover")
Undercover is the name of my application. We chose to use the port 8090
arbitrarily.
Now, here is how I initialize the connection client-side:
try {
server = (IServerGame) Naming.lookup("//"+address+":8090/undercover");
System.out.println("Connected to server " + address + ".");
} catch (Exception e) {
System.out.println("Connection failed.");
e.printStackTrace();
}
address is a string in the parameter of the method which initializes the connection and is the IP of the server. We ask the client to enter this IP to allow us to connect to different servers if we want.
When I run my application in local, whether I use localhost or my private IP 192.168.x.x as address, everything works fine. The client connects to the server and I can use the application. The problem is that when I want to use the application via WAN, sending the client to a friend and starting the server on my local machine, it doesn't work anymore. I get this error:
java.rmi.ConnectException: Connection refused to host: (private IP of host machine); nested exception is:
java.net.ConnectException: Connection timed out: connect
I've already checked a lot of posts in StackOverflow with the exact same problem and the usual answer is to either set the SystemProperty(java.rmi.server.hostname,"192.168.x.x") or do it via the -Djava.rmi.server.hostname in command line. I'm using Gradle to compile. I run the application via the run task. The client is a basic fx application too. None of this works unfortunately. I've also tried to open the port 8090 in my firewall but it doesn't solve the problem either.
Now maybe I'm doing this wrong. I've also tried to replace my private IP 192.168.x.x, which is IPv4 that I found via ipconfig in the command shell, with my public IP 79.95.x.x. But, again, it doesn't work.
I tried adding the SystemProperty(java.rmi.server.hostname,"192.168.x.x") like the first line of code that appears in the server code I showed you above.
I'm connected to internet via 4G. I don't have a box connection, so I can't really go to the box settings to allow certain ports, if that's ever a thing that could fix the issue.
EDIT :
So i've tried to switch from naming implementation in server-side to Registry implementation as it was suggested bellow but it didn't make any difference. As i thought it could be just a connection problem, i asked a friend to ping the server with telnet on the port 8090 and in fact it didn't work. He ran telnet [domain name or ip] [port] and the error was :
Unable to connect to remote host: Connection timed out
So the problem is that the external clients cannot reach my server or connect to the port. As i'm using 4G as internet connection as i mentioned above, any idea on how i could make the port reachable ?
Try using class java.rmi.registry.Registry rather than class java.rmi.Naming.
On the server side:
final int port = 8090;
Registry registry = LocateRegistry.createRegistry(port);
ServerGame serverGame = new ServerGame();
IServerGame stub = (IServerGame) UnicastRemoteObject.exportObject(serverGame, 0);
registry.bind("undercover", stub);
On the client side:
Registry registry = LocateRegistry.getRegistry("server host name or IP", 8090);
IServerGame serverGame = (IServerGame) registry.lookup("undercover");
I am attempting to establish a connection to my local sqlserver instance on android with this line
Connection conn = DriverManager.getConnection("jdbc:sqlserver://localhost:3306;DatabaseName=test", "admin", "password");
But I am getting this error
The TCP/IP connection to the host localhost, port 3306 has failed.
Error: "Connection refused. Verify the connection properties. Make
sure that an instance of SQL Server is running on the host and
accepting TCP/IP connections at the port. Make sure that TCP
connections to the port are not blocked by a firewall
I know that using jdbc to create direct database connections on android is not recommended for very good reasons, but that is not my concern right now.
I have verified in sql server configuration manager that tcp/ip is enabled for LOCAL and that IPAll TCP Port is set to 3306. I restarted the server after making these changes.
I have created a firewall rule allowing tcp/ip connections on port 3306 for local/domain connections inbound and outbound.
I checked the port with telnet telnet localhost 3306 and it connected.
Any help is appreciated, it is beginning to get frustrating.
I'm trying to make a connection to an already existing database in SQL Server 2012n with Netbeans 8.
Using the connection wizard I select Sql Server 2012 and enter the credentials and fields.
However I get the message that a connection cannot be established.
You can see screenshots of the entered fields:
I also tried using "localhost" instead of "STIJN" this didn't work. I also tried with the default port "1433". Also didn't worked, however what port should this be? Where can I see what port I'm using? Maybe the error lies in the port, otherwise I wouldn't know where I made a mistake.
Go to your SQL Server configuration manager -> SQL server network configuration -> protocols for SQLEXPRESS -> TCP/IP (double click on it for properties).
On protocol page set enabled to Yes.
On IP Addresses page, scroll to bottom.
TCP Dynamic Ports: 54629
TCP Port: 1433
Apply and ok.
Make a connection with:
Host: localhost
Port: 1433
Your credentials
Instance field = blank.
This should work.
I have a client server architecture project in android. I cant connect with my public IP to server. I closed firewall, and did the port redirection for server. My friend can connect from outside to my server, but i can't, why? how can it be?..
Thanks..
Which OS are you running your client server code. If Windows, look for c:\Windows\System32\drivers\etc\hosts, if it's linux go the /etc/hosts/ file
Open the file with sudo privileges.
Format:
<IP> <HOSTNAME>.<DOMAIN> <ALIAS>
Example:
127.0.0.1 localhost.localdomain localhost
Add your IP here with domain name. Your Domain Name can be anything and try again. Also your question is a bit vague. Please add more details such as your os env and what exactly are you trying to achieve?