Interview Questions

Example : Look for Local Ports

Java Network Programming - Sockets for Servers


(Continued from previous question...)

Example : Look for Local Ports

Example 11-1: Look for Local Ports

    import java.net.*;
    import java.io.*;
     
 public class LocalPortScanner {
     
public static void main(String[] args) {
        
for (int port = 1; port <= 65535; port++) 
{
     
          try {
          
// the next line will fail and drop into the 
catch block if there is already a server
running on the port//

 ServerSocket server = new ServerSocket(port);
          }
          catch (IOException e) {
 System.out.println("There is a server on port
      " + port + ".");
          } // end try
     
        } // end for
     
      }
      
    }

    Here's the output I got when running
     LocalPortScanner on my NT workstation:
     
 D:\JAVA\JNP2\examples\11>java LocalPortScanner
    There is a server on port 135.
    There is a server on port 1025.
    There is a server on port 1026.
    There is a server on port 1027.
    There is a server on port 1028.

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