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select_poll_echo_server.py
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100 lines (85 loc) · 3.54 KB
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#!/usr/bin/env python2
# -*- coding: UTF-8 -*-
import select
import socket
import sys
import Queue
# Create a TCP/IP socket
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setblocking(0)
# Bind the socket to the port
server_address = ('localhost', 10000)
print >> sys.stderr, 'starting up on %s port %s' % server_address
server.bind(server_address)
# Listen for incoming connections
server.listen(5)
# Keep up with the queues of outgoing messages
message_queues = {}
# Do not block forever (milliseconds)
TIMEOUT = 1000
# Commonly used flag setes
READ_ONLY = select.POLLIN | select.POLLPRI | select.POLLHUP
READ_WRITE = READ_ONLY | select.POLLOUT
# Set up the poller
poller = select.poll()
poller.register(server, READ_ONLY)
# Map file descriptors to socket objects
fd_to_socket = {server.fileno(): server, }
while True:
# Wait for at least one of the sockets to be ready for processing
print >> sys.stderr, '\nwaiting for the next event'
events = poller.poll(TIMEOUT)
for fd, flag in events:
# Retrieve the actual socket from its file descriptor
s = fd_to_socket[fd]
# Handle inputs
if flag & (select.POLLIN | select.POLLPRI):
if s is server:
# A "readable" server socket is ready to accept a connection
connection, client_address = s.accept()
print >> sys.stderr, 'new connection from', client_address
connection.setblocking(0)
fd_to_socket[connection.fileno()] = connection
poller.register(connection, READ_ONLY)
# Give the connection a queue for data we want to send
message_queues[connection] = Queue.Queue()
else:
data = s.recv(1024)
if data:
# A readable client socket has data
print >> sys.stderr, 'received "%s" from %s' % (data, s.getpeername())
message_queues[s].put(data)
# Add output channel for response
poller.modify(s, READ_WRITE)
else:
# Interpret empty result as closed connection
print >> sys.stderr, 'closing', client_address, 'after reading no data'
# Stop listening for input on the connection
poller.unregister(s)
s.close()
# Remove message queue
del message_queues[s]
elif flag & select.POLLHUP:
# Client hung up
print >> sys.stderr, 'closing', client_address, 'after receiving HUP'
# Stop listening for input on the connection
poller.unregister(s)
s.close()
elif flag & select.POLLOUT:
# Socket is ready to send data, if there is any to send.
try:
next_msg = message_queues[s].get_nowait()
except Queue.Empty:
# No messages waiting so stop checking for writability.
print >> sys.stderr, 'output queue for', s.getpeername(), 'is empty'
poller.modify(s, READ_ONLY)
else:
print >> sys.stderr, 'sending "%s" to %s' % (next_msg, s.getpeername())
s.send(next_msg)
elif flag & select.POLLERR:
print >> sys.stderr, 'handling exceptional condition for', s.getpeername()
# Stop listening for input on the connection
poller.unregister(s)
s.close()
# Remove message queue
del message_queues[s]