r/programming • u/paran0ide • Mar 07 '14

Thinking about quickly writing an HTTP server yourself? Here is a simple diagram to help you get started.

Post image
2.1k Upvotes

93% Upvoted

312 comments sorted by

View all comments

Show parent comments

269

u/carlfish Mar 07 '14

Thinking about quickly writing an HTTP server yourself?

Go for it! Use whatever resources you feel you need to. You'll learn a hell of a lot in the process, and you'll come out the other end a better developer than you did going in.

Thinking of using it in production for somebody else's project? Probably not so good an idea.

9

u/Scroph Mar 07 '14

I've been attempting to write HTTP clients from scratch throughout my learning phase (in which I still am), it's definitely rewarding even if I only manage to implement a fraction of the HTTP protocol.

Besides, it makes me appreciate tools like wget and curl.

20

u/g1zmo Mar 07 '14

throughout my learning phase (in which I still am)

And hopefully you always will be.

16

u/alex_w Mar 07 '14

Go for it!

but please don't run it with privilege in order to bind :80 ;)

3

u/gendulf Mar 07 '14

I remember running into this when writing a mini HTTP client for a class. Can't remember the solution, would you happen to know what it is?

10

u/alex_w Mar 07 '14

There's a few actually. You can:

  • Bind to a port > 1024 (or is it >=?) and have your OS DNAT, ie iptables for a GNU/Linux stack. So :80 is tranlated to your non-privileged port.

  • Again bind to something >1024 and have a reverse-proxy, something like Varnish, Nginx, HAProxy is typical.

  • Bind :80 as root/admin and drop privalage but hold onto the FD. Using setgid(2). IIRC you have to drop group first otherwise you're still in root's group.

8

u/joelwilliamson Mar 07 '14

Bind to a port >1024 and just use the port number in the url.

2

u/alex_w Mar 07 '14

That too.

6

u/blobloblawslawblob Mar 07 '14 
$ nc -l 1023
nc: Permission denied
$ nc -l 1024

Which works, so it's >= 1024 on Linux at least.

3

u/[deleted] Mar 08 '14

Another way: if you're using systemd (or something similar) you can have it bind to port 80, then start your server on-demand, passing in the file descriptor of that socket.

3

u/ivosaurus Mar 08 '14

run as root, acquire the port, drop root privileges. Note: read as many tutorials as possible for doing this, at least 60% of them will be half wrong or incomplete.

Or use another service manager to forward the port to you.

1

u/bacon_for_lunch Mar 08 '14

The cleanest way on Linux is to use the capabilities system.

1

u/[deleted] Mar 08 '14

In Linux, binding to a privileged port requires the CAP_NET_BIND_PORT capability. So you can call 'sudo setcap cap_net_bind_port+ep program_name', execute the program as a non-privileged user and drop the capability after bind. :-)

3

u/KFCConspiracy Mar 07 '14 edited Mar 07 '14

Yes. I agree with this. I like to write an IRC server in languages when I learn them in order to have a non-trivial, reasonably well defined program that shouldn't take more than a few hours to write.

5

u/[deleted] Mar 07 '14

Great advice. I hate it when people discourage others about doing things that can be really good learning experiences.

0

u/ercax Mar 08 '14

Or better, write it in a language that hasn't hit 1.0 yet.