Communication between python client and java server

Question

My aim is to send a message from python socket to java socket. I did look out on the resource mentioned above. However I am struggling to make the Python client talk to Java server. Mostly because (End of line) in python is different from that in java.

say i write from python client: message 1: abcd message 2: efgh message 3: q (to quit)

At java server: i receive message 1:abcdefghq followed by exception because the python client had closed the socket from its end.

Could anybody please suggest a solution for a consistent talk between java and python.

Reference I used: http://www.prasannatech.net/2008/07/socket-programming-tutorial.html

Update: I forgot to add, I am working on TCP.

My JAVA code goes like this:(server socket)

String fromclient;

ServerSocket Server = new ServerSocket (5000);

System.out.println ("TCPServer Waiting for client on port 5000");

while(true) 
{
    Socket connected = Server.accept();
    System.out.println( " THE CLIENT"+" "+ connected.getInetAddress() +":"+connected.getPort()+" IS CONNECTED ");

    BufferedReader inFromClient = new BufferedReader(new InputStreamReader (connected.getInputStream()));

    while ( true )
    {
        fromclient = inFromClient.readLine();

        if ( fromclient.equals("q") || fromclient.equals("Q") )
        {
            connected.close();
            break;
        }
        else
        {
            System.out.println( "RECIEVED:" + fromclient );
        } 
    }
}

My PYTHON code : (Client Socket)

client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(("localhost", 5000))

while 1:

    data = raw_input ( "SEND( TYPE q or Q to Quit):" )
    if (data <> 'Q' and data <> 'q'):
        client_socket.send(data)
    else:
        client_socket.send(data)
        client_socket.close()
        break;

OUTPUT::

ON PYTHON CONSOLE(Client):

SEND( TYPE q or Q to Quit):abcd ( pressing ENTER)

SEND( TYPE q or Q to Quit):efgh ( pressing ENTER)

SEND( TYPE q or Q to Quit):q ( pressing ENTER)

ON JAVA CONSOLE(Server):

TCPServer Waiting for client on port 5000

THE CLIENT /127.0.0.1:1335 IS CONNECTED

RECIEVED:abcdefghq

EOL is EOL ('\n') - I think you'll need to post the bare minimum of code that creates your error — KevinDTimm
– KevinDTimm, Commented Nov 15, 2010 at 14:27
Just a word of advice: String fromclient; is less efficient allocated there. Allocate it here: String fromclient = inFromClient.readLine(); Apart from that, the code is really nice. — Chris Dennett
– Chris Dennett, Commented Apr 20, 2011 at 18:08
@AmandeepChugh Please if any answer solve your problem, accept it. — PhoneixS
– PhoneixS, Commented Oct 1, 2014 at 10:00

Mateen Ulhaq · Accepted Answer · 2019-09-12 07:12:22Z

8

Append \n to the end of data:

client_socket.send(data + '\n')

edited Sep 12, 2019 at 7:12

Mateen Ulhaq

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answered Jan 19, 2011 at 7:27

Shital

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Comments

Ankit Shah · Accepted Answer · 2013-04-21 06:42:33Z

ya..you need to add '\n' at the end of the string in python client..... here's an example... PythonTCPCLient.py

`

#!/usr/bin/env python

import socket

HOST = "localhost"
PORT = 8080

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((HOST, PORT))

sock.sendall("Hello\n")
data = sock.recv(1024)
print "1)", data

if ( data == "olleH\n" ):
    sock.sendall("Bye\n")
    data = sock.recv(1024)
    print "2)", data

    if (data == "eyB}\n"):
        sock.close()
        print "Socket closed"

`

Now Here's the java Code: JavaServer.java `

 import java.io.*;
import java.net.*;

class JavaServer {
    public static void main(String args[]) throws Exception {
        String fromClient;
        String toClient;

        ServerSocket server = new ServerSocket(8080);
        System.out.println("wait for connection on port 8080");

        boolean run = true;
        while(run) {
            Socket client = server.accept();
            System.out.println("got connection on port 8080");
            BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
            PrintWriter out = new PrintWriter(client.getOutputStream(),true);

            fromClient = in.readLine();
            System.out.println("received: " + fromClient);

            if(fromClient.equals("Hello")) {
                toClient = "olleH";
                System.out.println("send olleH");
                out.println(toClient);
                fromClient = in.readLine();
                System.out.println("received: " + fromClient);

                if(fromClient.equals("Bye")) {
                    toClient = "eyB";
                    System.out.println("send eyB");
                    out.println(toClient);
                    client.close();
                    run = false;
                    System.out.println("socket closed");
                }
            }
        }
        System.exit(0);
    }
}

` Reference:Python TCP Client & Java TCP Server

riyasyash · Accepted Answer · 2016-04-23 08:24:19Z

here is a working code for the same: Jserver.java

import java.io.*;
import java.net.*;
import java.util.*;
public class Jserver{
public static void main(String args[]) throws IOException{
    ServerSocket s=new ServerSocket(5000);

    try{
        Socket ss=s.accept();
        PrintWriter pw = new PrintWriter(ss.getOutputStream(),true);
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedReader br1 = new BufferedReader(new InputStreamReader(ss.getInputStream()));
        //String str[20];
        //String msg[20];
        System.out.println("Client connected..");
        while(true)
        {
            System.out.println("Enter command:");
            pw.println(br.readLine());
            //System.out.println(br1.readLine());
        }
    }
    finally{}
    }
}

Client.py

import socket               # Import socket module

s = socket.socket()         # Create a socket object
host = socket.gethostname() # Get local machine name
port = 5000                # Reserve a port for your service.

s.connect((host, port))
while 1:
    print s.recv(5000)
    s.send("message processed.."+'\n')

s.close

Nikolay Frick · Accepted Answer · 2017-01-22 21:47:15Z

0

I know it is late but specifically for your case I would recommend RabbitMQ RPC calls. They have a lot of examples on their web in Python, Java and other languages:

https://www.rabbitmq.com/tutorials/tutorial-six-java.html

answered Jan 22, 2017 at 21:47

Nikolay Frick

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Comments

Procrastinator · Accepted Answer · 2022-10-10 06:47:23Z

0

for the people who are struggling with,

data = raw_input ( "SEND( TYPE q or Q to Quit):" )

your can also use .encode() to send the data

edited Oct 10, 2022 at 6:47

Procrastinator

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answered Oct 5, 2022 at 10:52

Tirth Patel

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