Tag: Open Source

From Rainer’s Blog. It looks syslog assumes data sent whenTCP send() was successful by design.

Simulated the behavior and confirmed by running below one in client mode & the other in server mode. When you kill the server process & run it again while client process is running, you’ll see a message lost.

import sys
import SocketServer
import socket
import time

def usage():
    print "%s [client | server]" % sys.argv[0]
    
def server(HOST, PORT):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.bind((HOST, PORT))
    sock.listen(1)
    (conn, sa) = sock.accept()
    try:
        while True:
            msg = conn.recv(8192)
            print "* received '%s'" % msg
            if len(msg) == 0:
                break;
    except socket.error, e:
        print 'Error: %s' % e
    
    conn.close()

def client_connect(HOST, PORT):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    try:
        sock.connect((HOST, PORT))
    except socket.error, e:
        print "Error: %s" % e
        return None
    
    return sock

def client(HOST, PORT):
    sock = None
    i = 0
    while i< 10:
        if sock == None:
            print "connecting..."
            sock = client_connect(HOST, PORT)
        if sock == None:
            print "no connection. sleeping..."
            time.sleep(3)
            continue
        
        data = "* hoge %d" % i
        print "sending %s" % data
        
        try:
            ret = sock.send(data)
            
            print "Sent:     %s, return: %d" % (data, ret)
            i = i + 1
        except socket.error, e:
            print 'Error: %s' % e
            sock.close()
            sock = None
        print "sleeping..."
        time.sleep(1)

    sock.shutdown(socket.SHUT_RDWR)
    sock.close()

def main():
    if len(sys.argv) != 2:
        usage()
        return

    HOST, PORT = "localhost", 9999

    if sys.argv[1].lower() == "server":
        print "running server..."
        server(HOST, PORT)
    else:
        print "running client..."
        client(HOST, PORT)

if __name__ == "__main__":
    main()

def sub_handler(sock, events):
    msg = sock.recv()
    print msg

def sub():
    print "*** sub"
    loop = ioloop.IOLoop.instance()
    ctx = zmq.Context()
    sock = ctx.socket(zmq.SUB)
    sock.connect('tcp://127.0.0.1:5555')
    sock.setsockopt(zmq.SUBSCRIBE, '')
    loop.add_handler(sock, sub_handler, zmq.POLLIN)
    loop.start()

def pub():
    print "*** pub"
    ctx = zmq.Context()
    sock = ctx.socket(zmq.PUB)
    sock.bind('tcp://127.0.0.1:5555')
    for i in range(0,10):
        msg = "[%d] Hello" % i
        print "publishing %s" % msg
        sock.send(msg)
        time.sleep(0.5)

ZeroMQ request/reply memo.
install:

sudo port install py-zmq

py:

import sys
import zmq
from zmq.eventloop import ioloop

def rep_handler(sock, events):
    msg = sock.recv()
    sock.send(msg)

def rep():
    print "*** rep"
    loop = ioloop.IOLoop.instance()
    ctx = zmq.Context()
    sock = ctx.socket(zmq.REP)
    sock.bind('tcp://127.0.0.1:5555')
    loop.add_handler(sock, rep_handler, zmq.POLLIN)
    loop.start()

def req():
    print "*** req"
    ctx = zmq.Context()
    sock = ctx.socket(zmq.REQ)
    sock.connect('tcp://127.0.0.1:5555')
    sock.send('hello')
    print sock.recv()

def main():
    command = sys.argv[1].lower()
    if command == "req":
        req()
    elif command == "rep":
        rep()

main()