Communication Java(Client) with Python(Server)

Question

I am doing a simple Java Client application which should communicate with Python Server. I can easily send a string to Python Server and print it in console, but when i'm trying to use received string in IFs it never get into IF statement even if it should.

Here is Java Client send msg code

        socket = new Socket(dstAddress, dstPort);
        dataOutputStream = new DataOutputStream(
            socket.getOutputStream());
        dataInputStream = new DataInputStream(socket.getInputStream());

        if(msgToServer != null){
            dataOutputStream.writeUTF("UP");
        }

        System.out.println(dataInputStream.readLine());

And Python Server code:

import socket

HOST = ''
PORT = 8888
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
s.listen(1)
print 'Socket now listening'

conn, addr = s.accept()
print 'Connected to: ' + addr[0] + ':' + str(addr[1])

data = conn.recv(1024)
if data == "UP":
     conn.sendall('Works')
else:
     conn.sendall('Does not work')
conn.close()
s.close()
print data

So when i send to Python Server "UP" it should send back to Java Client "Works", but i reveive "Does not work" and in Python Server the output data is: "UP"

Why it isn't go into if statement?

i print some 'data' info like: , length = 4 and print data = UP, what more can i do? — borecky, Nov 11 '15 at 16:16
makes sense when you look at George answer: 2bytes + the length = len 4. Everything after the first 2 bytes: data[2:] — Ward, Nov 11 '15 at 16:19

score 2 · Accepted Answer · answered Nov 11 '15 at 16:16

The JavaDoc of DataOutputStream#writeUTF(...) says:

First, two bytes are written to the output stream as if by the writeShort method giving the number of bytes to follow

In you python code your data value will be prefixed with two bytes for the length of the string to follow.

Communication Java(Client) with Python(Server)

1 Answers1

Linked