Why Am I Getting a 'Connection Refused' Error When Connecting to My TCP Server?

"Connection Refused" Error in TCP Connection: Analysis and Resolution

In the scenario described, a Java client program experiences a "java.net.ConnectException: Connection refused" error while attempting to connect to a TCP server. This exception indicates that the server is not accessible at the specified IP address and port.

To understand the root cause and resolve the issue, several factors must be considered:

• Incorrect IP Address or Port: Ensure that the IP address and port provided in the client code are correct and match those specified in the server code.
• Server Availability: Verify that the server is running and listening for connections. Check if the server is started and configured properly.
• Firewall/Network Restrictions: Make sure that firewalls or network rules do not block the connection between the client and server. Ensure that the necessary ports are allowed in both directions.
• Listen Backlog Queue (Windows Servers): On Windows servers, if the maximum number of pending connections (determined by the system's listen backlog queue size) is exceeded, new connection attempts will be rejected with the "Connection refused" error. Increase the backlog queue size if necessary.

In this specific case, it appears that the client is trying to connect to "localhost" on port 5000. Ensure that the server is running on that IP and port, and check for any firewall exceptions that may be blocking the connection.

If all these checks are satisfactory and the error persists, further investigation might be required to identify any underlying system or configuration issues that could be preventing the connection from being established.

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