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Sockets recv function on a new line

Posted on 2006-11-10
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Last Modified: 2010-04-16
Hi experts,

I'm writing a program that receives data from a server and prints it.. but I would like to do this line by line. That is, everytime the server sends me a line, I want the line printed. I'm not sure on how to do this though, the current method is "data = fsocket.recv(1024)", however my assumption is that only reads in 1024 bytes at a time. Is it possible to have it receive one line and not wait till the 1024 bytes are filled? Thanks..
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Question by:Tabris42
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RichieHindle earned 500 total points
ID: 17914999
recv(1024) will read *up to* 1024 bytes, blocking if there's nothing ready to read.  It won't wait for 1024 bytes - it will wait for *some* bytes.  You need to read those bytes then look for newlines youself.  (If recv returns an empty string, that means the socket has been closed by the other end.)

Here's an example script, which reads data until it has a line, then both prints that line and echoes it back to the client.

import socket, threading

def run():
    listener = socket.socket()
    listener.bind(('127.0.0.1', 1234))
    listener.listen(5)
    while 1:
        client, _ = listener.accept()
        worker_thread = threading.Thread(target=worker, args=(client,))
        worker_thread.setDaemon(True)
        worker_thread.start()

def worker(client):
    data = ""
    while 1:
        packet = client.recv(1024)
        if not packet:
            # The socket has been closed.
            break
       
        data += packet
        if chr(4) in data or chr(26) in data:
            # User has hit Ctrl+D or Ctrl+Z
            client.shutdown(2)
            client.close()
            break
       
        if '\n' in data:
            line, data = data.split('\n', 1)
            print line
            client.sendall(line+'\n')

if __name__ == '__main__':
    run()
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by:Tabris42
ID: 17915164
That's very helpful, thanks!
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