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select_echo_server.py
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90 lines (75 loc) · 2.82 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)
# Sockets from which we expect to read
inputs = [server]
# Sockets to which we expect to write
outputs = []
# Outgoing message queues (socket:Queue)
message_queues = {}
while inputs:
# Wait for at least one of the sockets to be ready for processing
print >>sys.stderr, '\nwaiting for the next event'
readable, writable, exceptional = select.select(inputs, outputs, inputs)
# Handle inputs
for s in readable:
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)
inputs.append(connection)
# 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
if s not in outputs:
outputs.append(s)
else:
# Interpret empty result as closed connection
print >>sys.stderr, 'closing', client_address, 'after reading no data'
# Stop listening for input on the connection
if s in outputs:
outputs.remove(s)
inputs.remove(s)
s.close()
# Remove message queue
del message_queues[s]
# Handle outputs
for s in writable:
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'
outputs.remove(s)
else:
print >>sys.stderr, 'sending "%s" to %s' % (next_msg, s.getpeername())
s.send(next_msg)
# Handle "exceptional conditions"
for s in exceptional:
print >>sys.stderr, 'handling exceptional condition for', s.getpeername()
# Stop listening for input on the connection
inputs.remove(s)
if s in outputs:
outputs.remove(s)
s.close()
# Remove message queue
del message_queues[s]