How to Resolve java.net.ConnectException: Connection Refused Error in Java

What can cause the java.net.ConnectException: failed to connect error in Java?

// Example that may trigger ConnectException
try {
    Socket socket = new Socket("192.168.253.3", 2468);
} catch (IOException e) {
    e.printStackTrace();
}

The `java.net.ConnectException: failed to connect` error occurs when a Java application tries to connect to a server but fails, often due to network issues or misconfigured server settings.

// Example of a try-catch block to handle the ConnectException error in Java
try {
    Socket socket = new Socket("192.168.253.3", 2468);
} catch (ConnectException e) {
    System.err.println("Failed to connect to server: " + e.getMessage());
} catch (IOException e) {
    System.err.println("General I/O exception: " + e.getMessage());
}

Causes

• The server is down or unreachable due to network issues.
• The port is not open on the server or firewall is blocking the connection.
• The IP address or hostname is incorrect.
• The server application is not running or listening on the specified port.

Solutions

• Ensure that the server at 192.168.253.3 is powered on and accessible.
• Use tools like `ping` or `traceroute` to diagnose network issues.
• Check if the server application is running and listening on port 2468 by using commands like `netstat -an | grep 2468` on the server.
• Verify firewall settings on the server to ensure that port 2468 is open for incoming connections.
• Double-check the IP address and make sure you are using the correct one.

Mistake: Assuming the server is always available without checking its status.

Solution: Always verify that the server is up and the application is running before attempting a connection.

Mistake: Not considering firewall rules that may block specific ports.

Solution: Check and configure the firewall rules to ensure proper access to necessary ports.

Mistake: Using the wrong IP address or hostname to connect.

Solution: Double-check the connection string for any typographical errors in the IP address.