Java Socket setKeepAlive() method

The setKeepAlive() method of Java Socket class returns a Boolean value 'true' if the write-half of the socket connection has been closed successfully else it returns false.

Syntax

Parameter

The parameter 'on' represents whether the socket should be enabled or not.

Return

Throws

SocketException - if an error is there in the underlying protocol, such as a TCP error.

Example 1

import java.io.IOException;
import java.net.*;
public class JavaSocketSetKeepAliveExample1  {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket();
        //enabling the boolean value true
        boolean on=true;
        //setKeepAlive() method either enables or disables the SO_KEEPALIVE option
        socket.setKeepAlive(on);
        //getKeepAlive() returns  a boolean indicating whether SO_KEEPALIVE option is enabled or not
        System.out.println("SO_KEEPALIVE is enabled: "+socket.getKeepAlive());
    }
}

Test it Now

Output:

SO_KEEPALIVE is enabled: true

Example 2

import java.io.IOException;
import java.net.*;
public class JavaSocketSetKeepAliveExample2  {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket();
        boolean on=false;
        //setKeepAlive() enables or disables the SO_KEEPALIVE option
        socket.setKeepAlive(on);
        //getKeepAlive() returns  a boolean indicating whether SO_KEEPALIVE option is enabled or not
        //by default the getKeepAlive value returns false
        if(socket.getKeepAlive()){
            System.out.println("SO_KEEPALIVE is enabled...");
        }
        else{
            System.out.println("SO_KEEPALIVE is not enabled");
        }
    }
}

Test it Now

Output:

SO_KEEPALIVE is not enabled...

Example 3

import java.io.IOException;
import java.net.*;
public class JavaSocketSetKeepAliveExample3  {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket();
        boolean on=false;
        //closing the socket
        socket.close();
        //setKeepAlive() enables or disables the SO_KEEPALIVE option
        //it will return an exception, as the socket is already closed
        socket.setKeepAlive(on);
        //getKeepAlive() returns  a boolean indicating whether SO_KEEPALIVE option is enabled or not
        System.out.println("SO_KEEPALIVE is enabled: "+socket.getKeepAlive());
    }
}

Test it Now

Output:

Exception in thread "main" java.net.SocketException: Socket is closed
	at java.net.Socket.setKeepAlive(Socket.java:1309)
	at com.javaTpoint.JavaSocketSetKeepAliveExample3.main(JavaSocketSetKeepAliveExample3.java:13)

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