Java - Socket getChannel() Method

Description

The Java Socket getChannel() returns the unique SocketChannel object associated with this socket, if any. A socket will have a channel if, and only if, the channel itself was created via the SocketChannel.open or ServerSocketChannel.accept methods.

Declaration

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

public SocketChannel getChannel()

Parameters

NA

Return Value

the socket channel associated with this socket, or null if this socket was not created for a channel.

Exception

NA

Example 1

The following example shows the usage of Java Socket getChannel() methd to get a unique SocketChannel object associated with this socket, if any. 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 channel using getChannel() method, 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("Channel: "+socket.getChannel()); 
      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 −

Channel: null
Port number: 6066
Inet Address: null

Example 2

The following example shows the usage of Java Socket getChannel() methd to get a unique SocketChannel object associated with this socket, if any. 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 channel using getChannel() method, 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("Channel: "+socket.getChannel());
      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 −

Channel: null
Port number: 49154
Inet Address: null

Example 3

The following example shows the usage of Java Socket getChannel() methd to get a unique SocketChannel object associated with this socket, if socket is already closed. As first step, we've created a Socket instance using no argument constructor. Using socket.close(), we're closing the socket and then using getChannel() method, 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.InetSocketAddress;
import java.net.Socket;

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

      System.out.println("Channel: "+socket.getChannel());
      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 −

Channel: null
Port number: -1
Inet Address: null