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I'm trying to connect to a server on local_host that does nothing more than accept and close the connection. On the client initiation of the connection, I'd like to connect to server with timeout.

Problem: By default, the connection timeout is 1 second, I'd like the connection timeout to be 0.001 seconds. If a connection can not be made within 0.001 seconds with the server(or server script not running) then timeout.

When I try to use settimeout(.001), I obtain unstable results while the server script is running. Sometimes the client script completes fast (as expected), other times the client script hangs (unexpected, since server is script is running). Oddly enough, if you run the client script on it's own (server NOT running) the script behaves stable.

When you remove settimeout(), the problem of unstable goes away all together (with active server script), but this also causes the connection timeout to default to 1 second (unwanted)

server.py

import socket
DEFAULT_CONFIG = {
 'address'   : 'localhost',
 'port'    : 8094,
 'buffer'   : 1023, # Read length
 'max_connections' : 700, # Max Number of concurrent connections
}
# start nonblocking server
s_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s_socket.setblocking(0)
s_socket.bind( (DEFAULT_CONFIG['address'] , DEFAULT_CONFIG['port']), )
s_socket.listen(DEFAULT_CONFIG['max_connections'] )
print ('server is now listening...')
# Outer Main Loop 
while(1):
 # normally other stuff can happen here
 # We're just going to assume as fast as possible
 # Inner loop -> grab as many connections as possible (in one go), and do nothing with them
 while(1):
  # accept and forget connection (allow client to close it)
  try:
   conn, addr = s_socket.accept()
   conn.close()
  except:
   break

client.py (to replicate problem, run this multiple times, with and without settimeout(.001))

import socket, time
DEFAULT_CONFIG = {
 'address'   : 'localhost',
 'port'    : 8094,
 'buffer'   : 1023, # Read length
}
# timer to keep track of how long this takes
time_start = time.time()
# open and close 100 connections WITH timeout 
for i in range(100):
 try:
  c_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  #c_socket.settimeout(.001)
  c_socket.connect( (DEFAULT_CONFIG['address'], DEFAULT_CONFIG['port']) )
  c_socket.setblocking(0)
  c_socket.close()
 except:
  pass
# how long it took to complete task
print(time.time()- time_start)
Farmer John
  • 9
  • 2
  • One millisecond is far too short for any network timeout. Why do you think you need this? – user207421 May 24 '20 at 06:17
  • I'm building a client/server socket pair over a local area network. I tested ping speed to be around tens of microseconds. I've also clocked python socket initiation speed over LAN to be around 1000/second (assuming server behaves perfectly), here I try to handle server drops by setting timeout, but then it starts behaving unstabe at initiation when I use settimeout(). My application requires these timeout speeds. – Farmer John May 25 '20 at 23:19
  • I'm making a REST-like server over LAN, and I'd like to query it as fast as possible using python. I've thought about persistent streaming connections, but figured REST-like is easier to scale for different data formats, and handle connection noise issues like a dropped/mutated byte (not just paranoid, I've had data blips occur from commercial server queries). – Farmer John May 25 '20 at 23:43

0 Answers0