Java Socket connect() method

connect(SocketAddress endpoint)

The connect() method of Java Socket class connects the specified socket to the server.

Syntax

Parameter

The parameter 'endpoint' represents the SocketAddress.

Return

Throws

IOException - if an error occurs during the connection.

IllegalBlockingModeException - if this socket has an associated channel and the channel is in non-blocking mode.

IllegalArgumentException - if the specified endpoint is null or if the SocketAddress subclass not supported by this socket.

Example 1

import java.io.IOException;
import java.net.*;
public class JavaSocketConnectExample1 {
    public static void main(String[] args) throws IOException {
      Socket socket = new Socket();
      InetAddress inetAddress=InetAddress.getByName("localhost");
      //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);
        //connect() method connects the specified socket to the server
        socket.connect(socketAddress);
        System.out.println("Inet address: "+socket.getInetAddress());
        System.out.println("Port number: "+socket.getLocalPort());
    }
}

Test it Now

Output:

Inet address: localhost/127.0.0.1
Port number: 1085

Example 2

import java.io.IOException;
import java.net.*;
public class JavaSocketConnectExample2 {
    public static void main(String[] args) throws IOException {
      Socket socket = new Socket();
      InetAddress inetAddress=InetAddress.getByName("localhost");
      //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);
        //connect() method connects the specified socket to the server
        socket.connect(socketAddress);
        System.out.println("Inet address: "+socket.getInetAddress());
        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.JavaSocketConnectExample2.main(JavaSocketConnectExample2.java:13)

Example 3

import java.io.IOException;
import java.net.*;
public class JavaSocketConnectExample3 {
    public static void main(String[] args) throws IOException {
      Socket socket = new Socket();
        //passing null argument in the SocketAddress
        SocketAddress socketAddress=null;
        //binding the  socket with the inetAddress and port number
        socket.bind(socketAddress);
        //connect() method connects the specified socket to the server
        socket.connect(socketAddress);
        System.out.println("Inet address: "+socket.getInetAddress());
        System.out.println("Port number: "+socket.getLocalPort());
    }
}

Test it Now

Output:

Exception in thread "main" java.lang.IllegalArgumentException: connect: The address can't be null
	at java.net.Socket.connect(Socket.java:560)
	at java.net.Socket.connect(Socket.java:538)
	at com.javaTpoint.JavaSocketConnectExample3.main(JavaSocketConnectExample3.java:13)

connect(SocketAddress endpoint, int timeout)

The connect() method of Java Socket class connects this socket to the server with the given timeout value. A zero timeout is inferred as an infinite timeout.

Syntax

Parameter

endpoint - it represents the SocketAddress.

timeout ? it represents the timeout value to be used in milliseconds.

Return

Throws

IOException - if an error occurs during the connection.

SocketTimeoutException - if timeout expires before connecting.

IllegalBlockingModeException - if this socket has an associated channel and the channel is in non-blocking mode.

IllegalArgumentException - if endpoint is null or is a SocketAddress subclass not supported by this socket.

Example 1

import java.io.IOException;
import java.net.*;
public class JavaSocketConnectExample4 {
    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);
        int timeout=1;
        //connect() method connects this socket to the server with the given timeout value.
        socket.connect(socketAddress,timeout);
        System.out.println("Inet address: "+socket.getInetAddress());
        System.out.println("Port number: "+socket.getLocalPort());
    }
}

Test it Now

Output:

Inet address: localhost/127.0.0.1
Port number: 1085

Example 2

import java.io.IOException;
import java.net.*;
public class JavaSocketConnectExample5 {
    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);
        //The timeout should be greater or equal to 0, else it will throw an exception
        int timeout=-10;
        //connect() method connects this socket to the server with the given timeout value.
        socket.connect(socketAddress,timeout);
        System.out.println("Inet address: "+socket.getInetAddress());
        System.out.println("Port number: "+socket.getLocalPort());
    }
}

Test it Now

Output:

Exception in thread "main" java.lang.IllegalArgumentException: connect: timeout can't be negative
	at java.net.Socket.connect(Socket.java:563)
	at com.javaTpoint.JavaSocketConnectExample5.main(JavaSocketConnectExample5.java:19)

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