Java - Socket bind() Method

Description

The Java Socket bind() method binds the socket to a local address. If the address is null, then the system will pick up an ephemeral port and a valid local address to bind the socket.

Declaration

Following is the declaration for java.net.Socket.bind() method.

public void bind(SocketAddress bindpoint) throws IOException

Parameters

bindpoint − the SocketAddress to bind to

Return Value

NA

Exception

IOException − if the bind operation fails, or if the socket is already bound.

IllegalArgumentException − if bindpoint is a SocketAddress subclass not supported by this socket.

SecurityException − if a security manager exists and its checkListen method doesn't allow the bind to the local port.

Example 1

The following example shows the usage of Java Socket bind() methd to bind the socket to localhost at port 6066. As first step, we've created a Socket instance using no argument constructor. Then in order to create a SocketAddress object, we've initialized an InetAddress instance of localhost address. Using InetSocketAddress object, we've created a SocketAddress object and then using bind() method, we bind the address to the socket. Once done, we're printing the local port and inetaddress as shown. In the end, we closed the socket using close() method.

package com.tutorialspoint;

import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;

public class SocketDemo {
   public static void main(String[] args) throws IOException {
      Socket socket = new Socket();  
      InetAddress inetAddress=InetAddress.getByName("localhost");  
      SocketAddress socketAddress=new InetSocketAddress(inetAddress, 6066);  
      socket.bind(socketAddress); 

      System.out.println("Port number: "+socket.getLocalPort()); 
      System.out.println("Inet Address: "+socket.getInetAddress()); 
      socket.close();
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Port number: 6066
Inet Address: null

Example 2

The following example shows the usage of Java Socket bind() methd to bind the socket to localhost at port 6066. As first step, we've created a Socket instance using no argument constructor. Now using bind() method, we bind a null address to the socket. Once done, we're printing the local port being assigned to the socket as default and inetaddress as shown. In the end, we closed the socket using close() method.

package com.tutorialspoint;

import java.io.IOException;
import java.net.Socket;

public class SocketDemo {
   public static void main(String[] args) throws IOException {
      Socket socket = new Socket();  
      socket.bind(null); 

      System.out.println("Port number: "+socket.getLocalPort()); 
      System.out.println("Inet Address: "+socket.getInetAddress()); 
      socket.close();
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Port number: 54383
Inet Address: null

Example 3

The following example shows the usage of Java Socket bind() methd to bind the socket to localhost at port 6066 if socket is already closed. As first step, we've created a Socket instance using no argument constructor. Then in order to create a SocketAddress object, we've initialized an InetAddress instance of localhost address. Using InetSocketAddress object, we've created a SocketAddress object. Using socket.close(), we're closing the socket and then using bind() method, we are trying to bind the address to the socket. It will throw an exception as shown below −

package com.tutorialspoint;

import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;

public class SocketDemo {
   public static void main(String[] args) throws IOException {
      Socket socket = new Socket();  
      InetAddress inetAddress=InetAddress.getByName("localhost");  
      SocketAddress socketAddress=new InetSocketAddress(inetAddress, 6066);
      socket.close();	  
      socket.bind(socketAddress); 

      System.out.println("Port number: "+socket.getLocalPort()); 
      System.out.println("Inet Address: "+socket.getInetAddress()); 
      socket.close();
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Exception in thread "main" java.net.SocketException: Socket is closed
	at java.base/java.net.Socket.bind(Socket.java:644)
	at com.tutorialspoint.SocketDemo.main(SocketDemo.java:15)