Java Socket getLocalPort() method

The getLocalPort() method of Java Socket class returns the local port number to which the specified socket is bound. If the socket was being closed, this method will return the connected port number after the socket is closed.

Syntax

Parameter

Return

The getLocalPort () method either returns the local port number to which the socket is connected, or returns -1 if the socket is not bounded.

Example 1

import java.io.IOException;
import java.net.*;
public class JavaSocketGetLocalPortExample1  {
    public static void main(String[] args) throws IOException {
      Socket socket = new Socket();
      InetAddress inetAddress=InetAddress.getByName(null);
      //the port should be greater or equal to 0, else it will throw an error
        int port=1085;
        //calling the constructor of the SocketAddress class
        SocketAddress socketAddress=new InetSocketAddress(inetAddress, port);
        //binding the  socket with the inetAddress and port number
        socket.bind(socketAddress);
        //getLocalPort() method returns the port number of the socket
        System.out.println("Port number: "+socket.getLocalPort());
    }
}

Test it Now

Output:

Port number: 1085

Example 2

import java.io.IOException;
import java.net.*;
public class JavaSocketGetLocalPortExample2  {
    public static void main(String[] args) throws IOException {
      Socket socket = new Socket();
        //getLocalPort() method returns the port number of the socket
      //returns -1 if the socket is not bounded
        System.out.println("Port number: "+socket.getLocalPort());
    }
}

Test it Now

Output:

Port number: -1

Example 3

import java.io.IOException;
import java.net.*;
public class JavaSocketGetLocalPortExample3  {
    public static void main(String[] args) throws IOException {
      Socket socket = new Socket();
      InetAddress inetAddress=InetAddress.getByName(null);
      //the port should be greater or equal to 0, else it will throw an error
        //passing negative port number
        int port=-1085;
        //calling the constructor of the SocketAddress class
        SocketAddress socketAddress=new InetSocketAddress(inetAddress, port);
        //binding the  socket with the inetAddress and port number
        socket.bind(socketAddress);
        //getLocalPort() method returns the port number of the socket
        System.out.println("Port number: "+socket.getLocalPort());
    }
}

Test it Now

Output:

Exception in thread "main" java.lang.IllegalArgumentException: port out of range:-1085
	at java.net.InetSocketAddress.checkPort(InetSocketAddress.java:143)
	at java.net.InetSocketAddress.(InetSocketAddress.java:188)
	at com.javaTpoint.JavaSocketGetLocalPortExample3.main(JavaSocketGetLocalPortExample3.java:13)

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