Python socket support/threading for client-server model

Question

So, I'm trying to write a very simple Client-Server system that places some congestion control over UDP. Simply, the server sends data packets and receives feedback packets from the client(s). I'm fairly new to this and am not certain about:

(1) How many users can be connected to the same socket?

(2) Can a socket be used by multiples users simultaneously (aka do reads/writes in parallel)?

(3) I need to use threading so that for each user, I can send data packets to them and receive feedback packets from them in parallel. I read in another post that one shouldn't be opening threads for each user (and I'm opening two threads per user). Am I wrong in doing this? Do I have an inherent misunderstanding? Does anyone have a suggestion for how to handle this?

Sorry, I'm very new to this.

joamag · Accepted Answer · 2013-03-29 01:01:12Z

2

(1) The number of connections to a socket is limited by the operative system but can go up to 100k and more check the C10K problem

(2) A socket may be used by multiple threads and even multiple processes using the pre-fork approach

(3) You may use a new thread per connection, but the best approach is to use a thread pool, alternatively you may use an asynchronous approach and avoid the use of threads

answered Mar 29, 2013 at 1:01

joamag

1,4721 gold badge10 silver badges15 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Steve P. Over a year ago

Could you please explain the pre-fork approach/thread pooling? Thanks.

joamag Over a year ago

In a thread pool approach you pre-create a series of threads (eg: 30) and then redirect work to them (eg: new data in connection) so that you don't need to create a new thread every time you get a new connection. The async approach bases itself on the fact that IO operations should not block the control flow and only "require" one thread. You can get more info at their wikipedia pages thread pool and async io.

A. Rodas · Accepted Answer · 2013-03-29 01:38:43Z

According to the documentation of socket.listen():

Listen for connections made to the socket. The backlog argument specifies the maximum number of queued connections and should be at least 0; the maximum value is system-dependent (usually 5), the minimum value is forced to 0.

So technically the request aren't processed in parallel but queued, until a usual maximum of 5. I don't know the reasons the author of the post you mention has to state that you shouldn't start a thread per user, but I have read that most servers use one thread per request. Also the thread pool is a common pattern, and it can be easily implemented using a syncronized object like Queue (this example may be useful if you want to see a small implementation).

Collectives™ on Stack Overflow

Python socket support/threading for client-server model

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related