title: recv() function too slow
body: <p>Hi i'm quite a newbie to Python. I' writting a simple LAN game (not simple for me) using a pygame module.</p>
  
  <p>Here's the problem - I have two computers (one old intel Atom netbook, the other intel i5 NTB). I want to achieve at least 5 FPS (the netbook is slowering the NTB, but not so much, now i have around 1,5 FPS), but calling recv() function twice a main loop takes total around 0,5 seconds on each machine. The wifi signal is strong and the router is 300Mbit/s and it sends a short roughly 500-character string. As you can see for measuring time i use time.clock().</p>
  
  <p>Here's the part of the "server" code, which i usually run on the i5 NTB:</p>
  
  <pre><code>while 1:
      start = time.clock()
      messagelen = c.recv(4)      #length of the following message (fixed 4 character)
      if " " in messagelen:
          messagelen = messagelen.replace(" ","")
      message = cPickle.loads(c.recv(int(messagelen))) #list of the arrows, other player position and changes in the game map
      arrowsmod = message[0]
      modtankposan = message[1]
      removelistmod = message[2]
      for i in removelistmod:
          try:
               randopos.remove(i)
          except ValueError:
              randopossv.remove(i)
  
      print time.clock()-start
  
  
      tosendlist=[]
      if len(arrows) == 0:  #if there are no arrows it appends only an empty list
          tosendlist.append([])
      else:
          tosendlist.append(arrows)
      tosendlist.append([zeltankpos, 360-angle])
      if len(removelist) == 0:   #if there are no changes of the map it appends only an empty list
          tosendlist.append([])
      else:
          tosendlist.append(removelist)
          removelist=[]
      tosend=cPickle.dumps(tosendlist)
      tosendlen = str(len(tosend))
      while len(tosendlen)&lt;4:
          tosendlen+=" "
      c.sendall(tosendlen)   #sends the length to client
      c.sendall(tosend)      #sends the actual message(dumped list of lists) to client
  
      ...something else which takes &lt;0,05 sec on the NTB
  </code></pre>
  
  <p>Here's the part of the "client" game code (just inverted the beginning - sending/receiving parts):</p>
  
  <pre><code>while 1:
      tosendlist=[]
      if len(arrows) == 0:  #if there are no arrows it appends only an empty list
          tosendlist.append([])
      else:
          tosendlist.append(arrows)
      tosendlist.append([zeltankpos, 360-angle])
      if len(removelist) == 0:   #if there are no changes of the map it appends only an empty list
          tosendlist.append([])
      else:
          tosendlist.append(removelist)
          removelist=[]
      tosend=cPickle.dumps(tosendlist)
      tosendlen = str(len(tosend))
      while len(tosendlen)&lt;4:
          tosendlen+=" "
      s.sendall(tosendlen)   #sends the length to server
      s.sendall(tosend)      #sends the actual message(dumped list of lists) to server
  
      start = time.clock()
      messagelen = s.recv(4)      #length of the following message (fixed 4 character)
      if " " in messagelen:
          messagelen = messagelen.replace(" ","")
      message = cPickle.loads(s.recv(int(messagelen))) #list of the arrows, other player position and changes in the game map
      arrowsmod = message[0]
      modtankposan = message[1]
      removelistmod = message[2]
      for i in removelistmod:
          try:
               randopos.remove(i)
          except ValueError:
              randopossv.remove(i)
  
      print time.clock()-start
      ... rest which takes on the old netbook &lt;0,17 sec
  </code></pre>
  
  <p>When I run let's say a single player version of the game on one machine (without the socket module) on the i5 NTB it has 50 FPS in the up left corner of the map and 25 FPS in the down right corner (the 1000x1000 pixel map contains 5x5 pixel squares, i think it's slower because of the bigger coordinates, but i can't believe that so much. BTW recv while ran as a LAN game in the down right corner of the map takes approx. the same time)
  on the Atom netbook it has 4-8 FPS.</p>
  
  <p>So could you please tell me, why it's so slow? The computers are not synchronized, one is faster, the other slower, but it can't be that they are waiting for each other, it would be max 0,17 secs delay, right? And plus the long recv calling would be only on the faster computer?
  Also I don't exactly know how the send/recv function work. It's weird the sendall takes literally no time while receiving takes 0,5 secs. Maybe sendall 
  is trying to send in the background while the rest of the program continues forward.</p>