How to Check If a Server is Online Using Java Code

How do I determine if a server is online using Java programming?

try {
    Socket socket = new Socket();
    socket.connect(new InetSocketAddress("example.com", 80), 2000);
    socket.close();
    System.out.println("Server is online.");
} catch (IOException e) {
    System.out.println("Server is offline.");
}

To check if a server is online in Java, you can establish a socket connection to the server's IP address at a specific port. If the connection is successful, the server is online; if an exception occurs, it is offline. This method is simple to implement and effective for checking server availability.

public class ServerStatus {
    public static void main(String[] args) {
        checkServerStatus("example.com", 80);
    }

    public static void checkServerStatus(String host, int port) {
        try (Socket socket = new Socket()) {
            socket.connect(new InetSocketAddress(host, port), 2000);
            System.out.println(host + " is online.");
        } catch (IOException e) {
            System.out.println(host + " is offline.");
        }
    }
}

Causes

• Server is offline due to maintenance or a crash.
• Incorrect IP address or hostname provided.
• Network issues preventing the connection.

Solutions

• Use the correct IP address or hostname for the server you are checking.
• Make sure the server is operational and accessible from your network.
• Increase the timeout period in case of slow responses.

Mistake: Using an incorrect port number for the service.

Solution: Ensure you are checking the correct port where the service is running, e.g., 80 for HTTP.

Mistake: Not handling exceptions appropriately.

Solution: Include exception handling to manage connection failures gracefully.