The ServerSocket class creates servers that listen for client programs to connect to them on published ports. The ServerSocket class is designed to be a "listener," which waits for clients to connect before doing anything.
Here are three of its constructors:
ServerSocket(int port) throws IOException
Creates server socket on the specified port with a queue length of 50.
ServerSocket(int port, int maxQueue) throws IOException
Creates a server socket on the specified port with a maximum queue length of maxQueue.
ServerSocket(int port, int maxQueue, InetAddress localAddress) throws IOException
Creates a server socket on the specified port with a maximum queue length of maxQueue. On a multihomed host, localAddress specifies the IP address to which this socket binds.
accept() method from ServerSocket is a blocking call that will wait for a client to initiate communications and return with a Socket that is then used for communication with the client.
import java.io.DataOutputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class MainClass {
public static void main(String args[]) {
try {
int port = 5555;
ServerSocket ss = new ServerSocket(port);
while (true) {
// Accept incoming requests
Socket s = ss.accept();
// Write result to client
OutputStream os = s.getOutputStream();
DataOutputStream dos = new DataOutputStream(os);
dos.writeInt(100);
s.close();
}
} catch (Exception e) {
System.out.println("Exception: " + e);
}
}
}