How to parse an HTTP request with `gen_tcp`?

Question

Below is part of one example explaining how to use gen_tcp. However, almost all of the tutorials will just show you an echo server, but none doing parsing of a real world HTTP request.

    handle_connect(Socket, BinaryList, Count) ->
    io:format("handle_connect ~p~n", [self()]),
    case gen_tcp:recv(Socket, 0) of
    {ok, Binary} ->
        io:format("request is :~s~n", Binary),
        case gen_tcp:send(Socket, Binary) of
            ok ->
                handle_connect(Socket, BinaryList, Count);
            {error, Reason} ->
                io:format("send failed~n"),
                gen_tcp:close(Socket)
        end;

I am curious about how one can parse the data in Erlang that is received by gen_tcp:recv/\[2,3\]. I skimmed through the code at lib/inets-5.7.1/src/http_server but there are too many modules, and I still can't figure out what the basics of parsing an HTTP request would be.

Can anyone show me how to parse an HTTP request, and what approach web frameworks take? Thanks~

See if this helps: https://stackoverflow.com/questions/43957164/erlang-gen-tcp-not-receiving-anything — 7stud, Jun 24 '18 at 18:29

score 4 · Answer 1 · edited Jun 23 '18 at 02:59

There are a couple of lightweight web server libraries for Erlang including:

Cowboy
MochiWeb
Misultin (not maintained anymore)

There is also Yaws which is more comparable to Apache. I would recommend checking out the code of Cowboy since it is very modular.

A shortcut to answer your question might be found here:

http://www.erlang.org/doc/man/erlang.html#decode_packet-3 and https://github.com/extend/cowboy/blob/master/src/cowboy_http_protocol.erl#L99

How to parse an HTTP request with `gen_tcp`?

1 Answers1