select python
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_addr = ('localhost', 10000)
print('starting server on {server_addr[0]}:{server_addr[1]}')
server.bind(server_address)
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('waiting 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(f'new connection from {client_address}')
connection.setblocking(False)
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(f'received "{data}" from {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(f'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(f'output queue for {s.getpeername()} is empty')
outputs.remove(s)
else:
print(f'sending "{next_msg}" to {s.getpeername()}')
s.send(next_msg)
# Handle "exceptional conditions"
for s in exceptional:
print(f'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]