java.net connectexception connection refused no further information, what should I do?

1) Client and Server, either or both of them are not in the network. Yes it's possible that they are not connected to LAN or internet or any other network, in that case, Java will throw java.net.ConnectException: Connection refused no further information exception on client side.

2) Server is not running The second most common reason is that the server is down and not running. In that case, also you will get java.net.ConnectException: Connection refused error. What I don't like is that the message it gives, no matter what is the reason it prints the same error. By the way, you can use the following networking commands e.g. ping to check if the server is running and listening on the port.

3) The server is running but not listening on the port, a client is trying to connect. This is another common cause of "java.net.ConnectException: Connection refused", where the server is running but listening on a different port. It’s hard to figure out this case, until you think about it and verify the configuration. If you are working on a large project and have a hierarchical configuration file, It's possible that either default configuration is taking place or some other settings are overriding your correct setting.

4) Firewall is not permitted for host-port combination Almost every corporate network is protected by firewalls. If you are connecting to some other companies network e.g. opening an FIX session to the broker, in any Electronic Trading System, then you need to raise firewall requests from both sides to ensure that they permit each other's IP address and port number. If the firewall is not allowing connection then also you will receive the same java.net.ConnectException: Connection refused exception in Java application.

5) Host Port combination is incorrect. This could be another reason for java.net.ConnectException: Connection refused: connect.It’s quite possible that either you are providing incorrect host port combination or earlier host port combination has been changed on the server side. Check the latest configuration on both client and server side to avoid connection refused exception.

6) Incorrect protocol in Connection String TCP is the underlying protocol for many high-level protocols including HTTP, RMI and others. While passing connection string, you need to ensure that you are passing correct protocol, which server is expecting e.g. if server has exposed its service via RMI than connection string should begin with rmi://