Question

Using the programming language of your choice, write a client application which: Connects to a network service, then Asks for version information, then Receives the response, then Disconnects and Prints out the response.

Detail:

The program will take no input from the user.

When your program is executed, it should connect to IP address 64.183.98.170 on port 3800. Upon successful connection, send the string:

version\n

where \n is an end of line marker.

The server will respond with a string and then disconnect. Your program should then also disconnect and print the result.

The output of your program should be the IP address and port number of the service you connected to with the version information the server responded with.

Answer 1

Server.java

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
//initialize socket and input stream
private Socket socket = null;
private ServerSocket server = null;
private DataInputStream incommingStream = null;
private String version = "";
private DataOutputStream outgoingtStream = null;
  
public Server(int portNumber)
{
// server starts: waits for client connection
try
{
server = new ServerSocket(portNumber);
System.out.println("Server: Service initiated at port: " + portNumber + "\nServer: Waiting for client connection...\n");
  
// accepts the incomming client connection
socket = server.accept();
System.out.println("Server: Connected with the client!\n");
  
// creating a channel to accept the client request string
incommingStream = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
  
// reading the client request
String clientLine = incommingStream.readUTF();
System.out.println("Server: Client communicated with " + clientLine + " request...");

// if the client string is "version"
if (clientLine.contains("version"))
{
version = System.getProperty("os.name") + ", Version " + System.getProperty("os.version");
}
else
{
version = "Unrecognized request!";
}
  
// creating a channel to send the response to the client
outgoingtStream = new DataOutputStream(socket.getOutputStream());
  
// writes the response string over the channel
outgoingtStream.writeUTF(version);
  
System.out.println("Server: Disconnected!");

//closing connection
socket.close();
incommingStream.close();
outgoingtStream.close();
}catch(IOException ex){
System.out.println("Server error: " + ex.getMessage());
}
}
  
public static void main(String[] args)
{
Server server = new Server(3800);
}
}

Client.java

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;

public class Client {
  
private Socket socket = null;
private DataInputStream incommingStream = null;
private DataOutputStream outgoingStream = null;
private String serverResponse = "";
  
public Client(String ipAddress, int portNumber)
{
// trying to establish a connection to the server through the provided IP Address and Port Number
try
{
socket = new Socket(ipAddress, portNumber);
System.out.println("Client: Connection established with the server!");
  
// creating a channel to send something to the server
outgoingStream = new DataOutputStream(socket.getOutputStream());
  
// the client request string
String clientString = "version\n";
System.out.println("Client: Sending query to the server...\n");
  
// sending the "version" request to the server
outgoingStream.writeUTF(clientString);
System.out.println("Client: sending completed!");
  
System.out.println("Client: Waiting for server response...\n");
  
// receives the server response over the input channel
incommingStream = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
  
// reading the server response
serverResponse = incommingStream.readUTF();
System.out.println("Client: Server responded with version: " + serverResponse);
  
System.out.println("Client: Disconnected!");
  
// closing connection
outgoingStream.close();
socket.close();
  
}catch(UnknownHostException ec){
System.out.println("Unknown host error: " + ec.getMessage());
}catch(IOException ex){
System.out.println("Connection error: " + ex.getMessage());
}
}
  
public static void main(String[] args)
{
Client client = new Client("127.0.0.1", 3800);
}
}

Note: First run the "Server.java" file and then run the "Client.java" file!