4 ms·

Python socket programming tutorial

88 points by silv3r_m00n 14y ago

rflrob 14y ago
Is there a reason to catch all those exceptions? If you're just sys.exit()ing anyways, why sacrifice all the traceback info?
- yk 14y ago
  You should always assume, that a best effort network fails. Therefore, you should always handle the exceptions ( even in a trivial example).
njharman 14y ago
Shouldn't the first step be install http://www.zeromq.org/ http://www.zeromq.org/? That is some seriously amazing stuff right there. Makes network programming (something I've avoided for years) almost trivial.
- lucian1900 14y ago
  More appropriately, the first step should be to install Twisted.
  - emidln 14y ago
    txZMQ is pretty cool if you are going the Twisted route. It's nice to reuse twisted's event loop instead of rolling your own.
  - pjscott 14y ago
    Or, if you'd rather stay out of Callback Hell, you could go with the alternate approach of not using Twisted. Personally, I'm a fan of Eventlet: http://eventlet.net/doc/ http://eventlet.net/doc/ I also hear good things about Gevent, which is similar, though not nearly as well-documented. Or just use vanilla Python; sometimes it's all you need.
- peterwwillis 14y ago
  The point is (or should be) to learn how socket programming works so you know what's going on under all that abstraction and why. That's also why we catch all those exceptions: so we understand why something failed, and how to deal with it in the future. It's also really fun to write complex networking apps from scratch =)
  - jwfergus 14y ago
    >It's also really fun to write complex networking apps from scratch I agree and disagree. It definitely is fun to write awesome complex code, in general, but I'm currently in the middle of developing a network application and the most frustrating part was the socket handling. Everything riding on top of these connections was fun, but actually working out the TCP logic was un-fun. That said, diff'rent strokes for diff'rent folks, I'm sure you're not the only one to love TCP coding, and I'm glad you guys exist to write tutorials for people like me :)
    - peterwwillis 14y ago
      I write modules to decode network protocols for fun. So yeah, maybe i'm not quite right in the head. On the other hand, it taught me about perverted networking standards like 802.1Q which is more common than you'd expect, and helps when you're trying to figure out why tcpdump isn't returning results you expected.
  - njharman 14y ago
    If that was the point we should all break out our chemistry sets to refine elements so we can create our logic chips and build up from there. At some point you have to admit you've climbed down enough turtles and it's time to get some shit done. I'm claiming ZeroMQ is far enough down. It's not that much abstraction. It's mostly avoiding you the annoyances and giving you framework of best practices.
    - aaronblohowiak 14y ago
      Each hacker choses how far down the rabbit hole they go, don't disparage others for going deeper.
- pjscott 14y ago
  You can't always choose the protocol you want. So no, the first step is not necessarily to use ZeroMQ, or HTTP, or Thrift, or whatever protocol you like best. Sometimes raw sockets are necessary.
djtriptych 14y ago
Decent tutorial, though I find the official Python HOWTO to be a more thorough and appropriate introduction to sockets for the complete newbie... http://docs.python.org/howto/sockets.html http://docs.python.org/howto/sockets.html
- obituary_latte 14y ago
  As a python newbie, I couldn't disagree more. I would have saved hours while working on (and possibly completed) the recent Stripe CTF. Frankly, I started to dislike the python docs thoroughly. However, I'm very much looking forward to the much-rumored new docs--I very much dig the language. As an example to my point, however, look at the two side-by-side as an aspiring tinkerer with the desire to send data over a socket. To me, the aforementioned tutorial is miles ahead of the python docs.
  - djtriptych 14y ago
    We may have an unreconcilable difference in philosophy here. I understand there is value in jumping straight to code, but I find real value in a (good) treatment of the model you're coding against before jumping in. Both tutorials are good, but I think a Python programmer totally new to network programming, which is the audience of the OP, is better served first reading that HOWTO before following the code samples...
    - obituary_latte 14y ago
      Understood. For me, I just can't learn that way--that's surely where the discrepancy is. I've never been able to, say, read one of those O'Reilly programming books all the way through (though I have bought a couple with the best of intentions). I just have to start playing around. It's probably not the right way, but its served me well. I think this is why the python docs don't work for me--they don't seem suited to that type of learning.
Myrmornis 14y ago
I really highly recommend "Foundations of Python Network Programming" by Brandon Rhodes and John Goerzen. It's just one of the best technical books I've read, from the opening example onwards. http://www.apress.com/9781430230038 http://www.apress.com/9781430230038
- deleted 14y ago
  [deleted]
peter_l_downs 14y ago
If you want to understand sockets, there's no excuse for not reading Beej's Guide to Network Programming [1]. It's C, not Python, but it covers all of the dirty details and explains exactly what's going on when you create a socket. For instance, this article never mentions that sockets are file descriptors — in Beej's article, it's right after the introduction (Section 2 [2]). How does this article describe a socket? > sockets are the fundamental "things" behind any kind of network communications done by your computer" Not very helpful. [1] http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html [2] http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html#theory http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html...
- xymostech 14y ago
  I came here to say just this. Anyone who wants to do real socket programming should learn some of the low level reasons for how sockets work behind the scenes. Plus, it's a great read! (I especially like his story about IPv6)

88 points by silv3r_m00n 14y ago

Is there a reason to catch all those exceptions? If you're just sys.exit()ing anyways, why sacrifice all the traceback info?

yk 14y ago
You should always assume, that a best effort network fails. Therefore, you should always handle the exceptions ( even in a trivial example).

njharman 14y ago

Shouldn't the first step be install http://www.zeromq.org/ http://www.zeromq.org/? That is some seriously amazing stuff right there. Makes network programming (something I've avoided for years) almost trivial.

lucian1900 14y ago
More appropriately, the first step should be to install Twisted.
- emidln 14y ago
  txZMQ is pretty cool if you are going the Twisted route. It's nice to reuse twisted's event loop instead of rolling your own.
- pjscott 14y ago
  Or, if you'd rather stay out of Callback Hell, you could go with the alternate approach of not using Twisted. Personally, I'm a fan of Eventlet: http://eventlet.net/doc/ http://eventlet.net/doc/ I also hear good things about Gevent, which is similar, though not nearly as well-documented. Or just use vanilla Python; sometimes it's all you need.
peterwwillis 14y ago
The point is (or should be) to learn how socket programming works so you know what's going on under all that abstraction and why. That's also why we catch all those exceptions: so we understand why something failed, and how to deal with it in the future. It's also really fun to write complex networking apps from scratch =)
- jwfergus 14y ago
  >It's also really fun to write complex networking apps from scratch I agree and disagree. It definitely is fun to write awesome complex code, in general, but I'm currently in the middle of developing a network application and the most frustrating part was the socket handling. Everything riding on top of these connections was fun, but actually working out the TCP logic was un-fun. That said, diff'rent strokes for diff'rent folks, I'm sure you're not the only one to love TCP coding, and I'm glad you guys exist to write tutorials for people like me :)
  - peterwwillis 14y ago
    I write modules to decode network protocols for fun. So yeah, maybe i'm not quite right in the head. On the other hand, it taught me about perverted networking standards like 802.1Q which is more common than you'd expect, and helps when you're trying to figure out why tcpdump isn't returning results you expected.
- njharman 14y ago
  If that was the point we should all break out our chemistry sets to refine elements so we can create our logic chips and build up from there. At some point you have to admit you've climbed down enough turtles and it's time to get some shit done. I'm claiming ZeroMQ is far enough down. It's not that much abstraction. It's mostly avoiding you the annoyances and giving you framework of best practices.
  - aaronblohowiak 14y ago
    Each hacker choses how far down the rabbit hole they go, don't disparage others for going deeper.
pjscott 14y ago
You can't always choose the protocol you want. So no, the first step is not necessarily to use ZeroMQ, or HTTP, or Thrift, or whatever protocol you like best. Sometimes raw sockets are necessary.

djtriptych 14y ago

Decent tutorial, though I find the official Python HOWTO to be a more thorough and appropriate introduction to sockets for the complete newbie... http://docs.python.org/howto/sockets.html http://docs.python.org/howto/sockets.html

obituary_latte 14y ago
As a python newbie, I couldn't disagree more. I would have saved hours while working on (and possibly completed) the recent Stripe CTF. Frankly, I started to dislike the python docs thoroughly. However, I'm very much looking forward to the much-rumored new docs--I very much dig the language. As an example to my point, however, look at the two side-by-side as an aspiring tinkerer with the desire to send data over a socket. To me, the aforementioned tutorial is miles ahead of the python docs.
- djtriptych 14y ago
  We may have an unreconcilable difference in philosophy here. I understand there is value in jumping straight to code, but I find real value in a (good) treatment of the model you're coding against before jumping in. Both tutorials are good, but I think a Python programmer totally new to network programming, which is the audience of the OP, is better served first reading that HOWTO before following the code samples...
  - obituary_latte 14y ago
    Understood. For me, I just can't learn that way--that's surely where the discrepancy is. I've never been able to, say, read one of those O'Reilly programming books all the way through (though I have bought a couple with the best of intentions). I just have to start playing around. It's probably not the right way, but its served me well. I think this is why the python docs don't work for me--they don't seem suited to that type of learning.

Myrmornis 14y ago

I really highly recommend "Foundations of Python Network Programming" by Brandon Rhodes and John Goerzen. It's just one of the best technical books I've read, from the opening example onwards. http://www.apress.com/9781430230038 http://www.apress.com/9781430230038

deleted 14y ago
[deleted]

peter_l_downs 14y ago

If you want to understand sockets, there's no excuse for not reading Beej's Guide to Network Programming [1]. It's C, not Python, but it covers all of the dirty details and explains exactly what's going on when you create a socket. For instance, this article never mentions that sockets are file descriptors — in Beej's article, it's right after the introduction (Section 2 [2]). How does this article describe a socket? > sockets are the fundamental "things" behind any kind of network communications done by your computer" Not very helpful. [1] http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html [2] http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html#theory http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html...

xymostech 14y ago
I came here to say just this. Anyone who wants to do real socket programming should learn some of the low level reasons for how sockets work behind the scenes. Plus, it's a great read! (I especially like his story about IPv6)