client / server (communication problem...)

[mark smith]

hi

i need to create a little client/server (multithread)

i read
http://java.sun.com/docs/books/tutorial/networking/sockets/clientServer.html

i don't need the protocol class (just need to return what the client type and the number of request...)

the connection is ok but when the client type... nothing happen on the server

client class

import java.io.*;
import java.net.*;
 
public class Client {
    public static void main(String[] args) throws IOException {
 
        Socket kkSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;
 
        String serverHostname = new String ("127.0.0.1");
 
        try {
            kkSocket = new Socket(serverHostname, 4444);
            out = new PrintWriter(kkSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Hote inconnue:" + serverHostname);
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Incapable de se connecteur au serveur:" + serverHostname);
            System.exit(1);
        }
 
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
 
       System.out.println("client1");
 
        String fromServer;
        String fromUser;
 
        while ((fromServer = in.readLine()) != null) {
            System.out.println("Serveur: " + fromServer);
            if (fromServer.equals("Bye."))
                break;
 
            fromUser = stdIn.readLine();
            if (fromUser != null) {
                System.out.println("Client: " + fromUser);
                out.println(fromUser);
            }
        }
 
        out.close();
        in.close();
        stdIn.close();
        kkSocket.close();
    }
}

server class

import java.net.*;
import java.io.*;
 
public class Server {
 
    private int nbRequete=0;
 
    public int ajouterRequete(){
            return nbRequete++;
    }
 
    public int getRequete(){
      return nbRequete;
    }
 
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        boolean listening=true;
 
        Server server = new Server();
 
        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println("Impossible d'�couter sur le port: 4444.");
            System.exit(-1);
        }
 
        while (listening)
          new ServerThread(serverSocket.accept(),server).start();
        serverSocket.close();
    }
}

ServerThread class

import java.net.*;
import java.io.*;
 
public class ServerThread extends Thread {
    private Socket socket = null;
 
   private Server server;
 
    public ServerThread(Socket socket,Server server) {
          super("ServerThread");
          this.socket = socket;
          this.server = server;
    }
 
    public void run() {
      try {
        System.out.println("a l'�coute");
        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        System.out.println("a l'�coute2");
        String inputLine, outputLine;
        while ((inputLine = in.readLine()) != null)
        {
          System.out.println ("Serveur: " + inputLine);
          server.ajouterRequete();
          outputLine= inputLine.toUpperCase();
          out.println(outputLine+ " Requete: "+ server.getRequete());
          if (outputLine.equals("Bye."))
            break;
        }
        out.close();
        in.close();
        //socket.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
}

PrintWriter and BufferedReader seem ok...
any idea?

[Anonymous]

hi marc,

the server code is fine - you may test it by connecting to your server with a telnet client and then typing a line.

however, the client expects the server to send a welcome string once they are connected. it hangs at:

        while ((fromServer = in.readLine()) != null) {

because the server also waits for the client to send something, which doesn't happen!

[mark smith]

ok but how can i resolve the problem

[Anonymous]

check this out.
like this, there is no loop or so, but you can see what you type in at the client will be received by the server. Now just do whatever you wanted to do with the data coming in at the server.
One caveat. When you run the client from an IDE, you might get problems because sometimes, STDIN (java.lang.System.in) is not readable (BufferedReader.readLine() in the client then returns immediately). I have this problem when I use my Netbeans IDE. Netbeans uses Ant for running a project, and by default you don't have a console (there is some kind of switch you can set in the "java" ant task, it's attribute "fork" which you probably have to set to "true" if you wanna use the Netbeans console as STDIN; see manual: http://ant.apache.org/manual/index.html). I recommend testing from the command line.

 
import java.io.*;
import java.net.*;
 
public class Client {
    public static void main(String[] args) throws IOException {
 
        Socket kkSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;
 
        String serverHostname = new String ("127.0.0.1");
 
        try {
            kkSocket = new Socket(serverHostname, 4444);
            out = new PrintWriter(kkSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Hote inconnue:" + serverHostname);
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Incapable de se connecteur au serveur:" + serverHostname);
            System.exit(1);
        }
 
        // if we get here we're connected (no exception was thrown at "new Socket(..)")
        
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
 
        System.out.println("client1");
 
        String fromServer;
        String fromUser;
 
        System.out.println("before readline");
        // !!! this call will not block when run via unmodified Netbeans+Ant 
        fromUser = stdIn.readLine(); 
        System.out.println("after readline");
        if (fromUser != null) {
            System.out.println("Client: " + fromUser);
            out.println(fromUser);
        }
 
        out.close();
        in.close();
        stdIn.close();
        kkSocket.close();
    }
}
 

[ September 28, 2005: Message edited by: Dennis K�hn ]

[sama xxx]

I have done this and am facing the same problem "client don't get the result from the server".....need help


Client code:

 package Client;
 
import java.io.*;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
 
public class Client {
 
public static void main(String[] args) throws IOException {
 
        Socket kkSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;
 
        try {
            kkSocket = new Socket("CCITGP200105047.aa.uaeu.ac.ae",7909 );
        
        System.out.println("Enter the Customer ID" );
           out = new PrintWriter(kkSocket.getOutputStream(), true);
        
          in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
        
        
        } catch (UnknownHostException e) {
            System.err.println("Don't know about host: CCITGP200105047.aa.uaeu.ac.ae.");
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for the connection to: CCITGP200105047.aa.uaeu.ac.ae.");
            System.exit(1);
        }
 
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        
        String userInput;
 
while ((userInput = stdIn.readLine()) != null) {
    out.println(userInput);
    System.out.println("Account info: " + in.readLine());
}
 
        out.close();
        in.close();
        stdIn.close();
        kkSocket.close();
        
}
}      

Multi-Server code:

 package Server;
 
import java.net.*;
import java.io.*;
 

 
public class Multiserver{
 

public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
        boolean listening = true;
 
        try {
            serverSocket = new ServerSocket(7909,16);
            
        } catch (IOException e) {
            System.err.println("Could not listen on port:7909.");
            System.exit(1);
        }
 
        while (listening)
        
    new Serverthread(serverSocket.accept()).start();
 
        serverSocket.close();
        
    }
}
 

 

Thread code:

 package Server;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
 

public class Serverthread extends Thread{

private Socket socket = null;

 
    public Serverthread(Socket socket) {
super("ServerThread");
this.socket = socket;
    }
 
    public void run() {
 
     
try {
    PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
    BufferedReader in = new BufferedReader(
    new InputStreamReader(
    socket.getInputStream()));
 
    //String outputLine=null;
  
       String input;
        // out.println(outputLine);
        while ((input = in.readLine()) != null) {
        
        CheckBalance(input);
        }
        

    out.close();
    in.close();
    socket.close();
 
} catch (IOException e) {
    e.printStackTrace();
}
   }
public static void CheckBalance(String a)
{
  Connection con = null ;
 
    try
    {
 
  /* MySQL */
        String databaseURL="jdbc:mysql://localhost/ATM" ;
        String driverName="com.mysql.jdbc.Driver" ;
        String user="" ;
        String password="" ;
 
    
      Class.forName ( driverName ).newInstance();
 
      con = DriverManager.getConnection ( databaseURL , user , password );
 
      if ( ! con.isClosed() )
      System.out.println ( "Successfully connected to the DataBase Server..." );
      
      
        Statement   statement ;
 
        statement = con.createStatement();
 
        String selectQuery = "SELECT Firstname,Lastname,Accountnumber,CustomerId,Balance FROM CUSTOMER" ;
 
        ResultSet resultSet = statement.executeQuery ( selectQuery );
 

        if ( resultSet != null ) // Succes
        {
 
                while ( resultSet.next() )
                {
                StringFirstname=( String ) resultSet.getObject ( "Firstname" ) ;
                StringLastname=( String ) resultSet.getObject ( "Lastname" ) ;
                StringAccountnumber=( String ) resultSet.getObject ( "Accountnumber" ) ;
                        StringCustomerId=( String ) resultSet.getObject ( "CustomerId" ) ;
                        StringBalance=( String ) resultSet.getObject ( "Balance" ) ;
                        
                        if(CustomerId.equals(a)){
                        System.out.println ( "-----------------------------------" );
                        System.out.println ( "Firstname = " + Firstname); 
                        System.out.println ( "Lastname = " + Lastname); 
                        System.out.println ( "AccountNumber = " + Accountnumber); 
                        System.out.println ( "Customer Id = " + CustomerId); 
                        System.out.println ( "Dear Customer "  +  Firstname + " " + Lastname  +  " Your Account Balance is = " + Balance);
                        }
                }
 
                resultSet.close() ;
        }
        //
        else 
          System.out.println ( "INVALID ACCOUNT NUMBER PLEASE INSERT A VALID ACCOUNT NUMBER "    );
         
        
        
        
        
        statement.close();

      if ( con != null )
        con.close();
 
    }
    catch ( Exception e )
    {
      System.err.println ( "Exception: " + e.getMessage() );
    }
}
   }
 

i have changed things according to the previous explenation but still

[Ernest Friedman-Hill]

Colinm and sama xxx

Both of you, welcome to JavaRanch!

And I do have to let you know that you're both in violation of the JavaRanch policy on display names. It requires that you use a full, real (sounding) first and last name for your display name. Joke names and "handles" aren't acceptable at the Ranch. You can change your display names here; please do so right away. Thanks for your cooperation.

[sama Ali]

LOL no one seems to offer help in here