Java - Socket close() Method

Description

The Java Socket close() method closes this socket. Any thread currently blocked in an I/O operation upon this socket will throw a SocketException. Once a socket has been closed, it is not available for further networking use (i.e. can't be reconnected or rebound). A new socket needs to be created. Closing this socket will also close the socket's InputStream and OutputStream. If this socket has an associated channel then the channel is closed as well.

Declaration

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

public void close() throws IOException

Parameters

NA

Return Value

NA

Exception

IOException − if an I/O error occurs when closing this socket.

Example 1

The following example shows the usage of Java Socket close() methd to close the socket after binding 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 close() methd to close the socket after binding 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 close the socket before bind() operation to localhost at port 6066 to check the impact of close operation. 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()); 
   }
}

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)