Build a simple HTTP server in C

Question

I need to build a simple HTTP server in C. Any guidance? Links? Samples?

I got the same question and somehow I got incomplete but very simple implementation(incomplete) using C, which compiles under Ubuntu linux thought it would be valuable if I tag it here, https://blog.abhi.host/blog/2010/04/15/very-simple-http-server-writen-in-c/ — Pulathisi Bandara, Feb 04 '18 at 19:39

Ates Goral · Answer 1 · 2013-10-12T15:10:02.290

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I'd recommend that you take a look at: A Practical Guide to Writing Clients and Servers

What you have to implement in incremental steps is:

Get your basic TCP sockets layer running (listen on port/ports, accept client connections and send/receive data).
Implement a buffered reader so that you can read requests one line (delimited by CRLF) at a time.
Read the very first line. Parse out the method, the request version and the path.
Implement header parsing for the "Header: value" syntax. Don't forget unfolding folded headers.
Check the request method, content type and content size to determine how/if the body will be read.
Implement decoding of content based on content type.
If you're going to support HTTP 1.1, implement things like "100 Continue", keep-alive, chunked transfer.
Add robustness/security measures like detecting incomplete requests, limiting max number of clients etc.
Shrink wrap your code and open-source it :)

edited Oct 12 '13 at 15:10

answered Oct 06 '08 at 22:35

Ates Goral

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Point #9, especially after posting a question here, +1 :) – Matthieu Nov 19 '16 at 23:04
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Thank you for providing concepts rather than prebuilt solutions or links to RFC and Sockets. Reading the RFC and learning about Sockets isn't enough to build your own web server if you don't have these concepts in mind. – Stanley Sathler Dec 13 '20 at 15:13
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Reading requests line by line using "*a buffered reader*" (hence storing the line in a buffer until we find a CRLF), makes me anxoius about attacks that send gigabytes of data without CRLF. For this, I usually read using 'states', re-allocate the buffers on the go with the data, check for limits every read and send 414 appropriately. Except point #2, I agree with all the other points. – Example person Feb 20 '22 at 08:20

score 97 · Accepted Answer · edited Oct 07 '21 at 05:46

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I suggest you take a look at tiny httpd. If you want to write it from scratch, then you'll want to thoroughly read RFC 2616. Use BSD sockets to access the network at a really low level.

edited Oct 07 '21 at 05:46

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answered Oct 06 '08 at 22:13

Adam Rosenfield

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Or use inetd and skip the networking part. – jrockway Dec 30 '09 at 07:21
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Don't read [RFC 2616](http://tools.ietf.org/html/rfc2616) now, it obsoleted by: [RFC 7230](http://tools.ietf.org/html/rfc7230), [RFC 7231](http://tools.ietf.org/html/rfc7231), [RFC 7232](http://tools.ietf.org/html/rfc7232), [RFC 7233](http://tools.ietf.org/html/rfc7233), [RFC 7234](http://tools.ietf.org/html/rfc7234), [RFC 7235](http://tools.ietf.org/html/rfc7235) – songhir Jun 10 '14 at 12:53
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`tiny httpd` is also on github here: https://github.com/larryhe/tinyhttpd – Purplejacket Aug 30 '17 at 21:25

score 39 · Answer 3 · edited Jun 23 '18 at 15:53

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An HTTP server is conceptually simple:

Open port 80 for listening
When contact is made, gather a little information (get mainly - you can ignore the rest for now)
Translate the request into a file request
Open the file and spit it back at the client

It gets more difficult depending on how much of HTTP you want to support - POST is a little more complicated, scripts, handling multiple requests, etc.

But the base is very simple.

edited Jun 23 '18 at 15:53

vallentin

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answered Oct 06 '08 at 22:15

Adam Davis

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Thank you for providing concepts rather than prebuilt solutions or links to RFC and Sockets. Reading the RFC and learning about Sockets isn't enough to build your own web server if you don't have these concepts in mind. – Stanley Sathler Dec 13 '20 at 15:11

score 30 · Answer 4 · edited Apr 09 '13 at 14:45

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Mongoose (Formerly Simple HTTP Daemon) is pretty good. In particular, it's embeddable and compiles under Windows, Windows CE, and UNIX.

edited Apr 09 '13 at 14:45

Samuel Katz

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answered Oct 06 '08 at 22:30

Bob Nadler

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score 13 · Answer 5 · answered Oct 06 '08 at 22:12

Open a TCP socket on port 80, start listening for new connections, implement this. Depending on your purposes, you can ignore almost everything. At the easiest, you can send the same response for every request, which just involves writing text to the socket.

XP1 · Answer 6 · 2021-11-02T23:15:28.843

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Look at nweb (Nigel's Web Server), "a tiny, safe web server [...] with only 200 lines of C source code":

https://drive.google.com/file/d/0B3msld7qnNOhN1NXaFIwSFU2Mjg/view?usp=sharing&resourcekey=0-ngY0neP78dxJKlFv0PJoDQ ~~http://www.ibm.com/developerworks/systems/library/es-nweb/~~

The article includes pseudocode, explanations, and comments.

EDIT: IBM's link has died. I have saved a PDF of the webpage to Google Drive. Here is the code download:

https://drive.google.com/file/d/0B3msld7qnNOhSGZGdDJJMmY0VHM/view?usp=sharing&resourcekey=0-xkbf4mv0gN1sZrhBjt86UQ

@ankushagarwal has made a few changes and uploaded his version on GitHub: https://github.com/ankushagarwal/nweb

edited Nov 02 '21 at 23:15

answered Aug 26 '12 at 18:44

XP1

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Eh up voted without checking link :/ I'm looking for the exact thing you mentioned, if you find something can you ping me? Txt – samayo Jun 30 '16 at 18:59
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@samayo IBM's link has died. I have provided some mirrors. – XP1 Jul 01 '16 at 00:01
Here's a mirror by archive.org - which will hopefully be around for years to come: https://web.archive.org/web/20140905115151/http://www.ibm.com/developerworks/systems/library/es-nweb/ – james246 Oct 21 '16 at 10:50

Daniel A. White · Answer 7 · 2008-10-06T22:30:41.813

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I have written my own that you can use. This one works has sqlite, is thread safe and is in C++ for UNIX.

You should be able to pick it apart and use the C compatible code.

http://code.google.com/p/mountain-cms/

edited Oct 06 '08 at 22:30

answered Oct 06 '08 at 22:12

Daniel A. White

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score 5 · Answer 8 · answered Oct 06 '08 at 22:38

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The HTTP spec and Firebug were very useful for me when I had to do it for my homework.

Good luck with yours. :)

answered Oct 06 '08 at 22:38

Omer van Kloeten

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score 4 · Answer 9 · answered Oct 06 '08 at 22:12

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I'd suggest looking at the source to something like lighthttpd.

answered Oct 06 '08 at 22:12

warren

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score 2 · Answer 10 · answered Oct 07 '08 at 01:23

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http://www.manning.com/hethmon/ -- "Illustrated Guide to HTTP by Paul S. Hethmon" from Manning is a very good book to learn HTTP protocol and will be very useful to someone implementing it /extending it.

answered Oct 07 '08 at 01:23

anjanb

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score 2 · Answer 11 · edited May 23 '17 at 12:02

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There is a duplicate with more responses.

One candidate not mentioned yet is spserver.

edited May 23 '17 at 12:02

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answered Dec 30 '09 at 07:17

akauppi

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score 1 · Answer 12 · answered Oct 06 '08 at 22:13

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Use platform specific socket functions to encapsulate the HTTP protocol, just like guys behind Apache did.

answered Oct 06 '08 at 22:13

arul

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But... Apache Server is the complete opposite of "simple"? – HackerDaGreat57 Dec 05 '22 at 22:22

Build a simple HTTP server in C

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