java.net.NoRouteToHostException: No route to host (Host unreachable)

This exception is thrown when the network is unable to establish a connection between the client and server, typically because the server is not reachable or the network path is blocked. This can happen due to various reasons such as incorrect IP address, incorrect port number, firewall blocking the connection, or network connectivity issues.

To resolve this issue, you can try the following steps:

1. Check if the server is up and running and reachable from your network. You can try pinging the server IP address to verify the connectivity.

2. Verify if you are using the correct IP address and port number to connect to the server.

3. Check if there is any firewall blocking the connection. You can try disabling the firewall temporarily to see if it resolves the issue.

4. Check if there are any network connectivity issues such as DNS resolution failure, network congestion, or routing issues. You can try troubleshooting the network connectivity using network diagnostic tools.

5. If none of the above steps work, you may need to contact your network administrator or internet service provider for further assistance.