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diff --git a/guide/getting_started.md b/guide/getting_started.md new file mode 100644 index 0000000..812b1e0 --- /dev/null +++ b/guide/getting_started.md @@ -0,0 +1,80 @@ +Getting started +=============== + +Cowboy does nothing by default. + +Cowboy requires the `crypto` and `ranch` applications to be started. + +``` erlang +ok = application:start(crypto). +ok = application:start(ranch). +ok = application:start(cowboy). +``` + +Cowboy uses Ranch for handling the connections and provides convenience +functions to start Ranch listeners. + +The `cowboy:start_http/4` function starts a listener for HTTP connections +using the TCP transport. The `cowboy:start_https/4` function starts a +listener for HTTPS connections using the SSL transport. + +Listeners are a group of processes that are used to accept and manage +connections. The processes used specifically for accepting connections +are called acceptors. The number of acceptor processes is unrelated to +the maximum number of connections Cowboy can handle. Please refer to +the [Ranch guide](http://ninenines.eu/docs/en/ranch/HEAD/guide/toc) +for in-depth information. + +Listeners are named. They spawn a given number of acceptors, listen for +connections using the given transport options and pass along the protocol +options to the connection processes. The protocol options must include +the dispatch list for routing requests to handlers. + +The dispatch list is explained in greater details in the +[Routing](routing.md) chapter. + +``` erlang +Dispatch = cowboy_router:compile([ + %% {URIHost, list({URIPath, Handler, Opts})} + {'_', [{'_', my_handler, []}]} +]), +%% Name, NbAcceptors, TransOpts, ProtoOpts +cowboy:start_http(my_http_listener, 100, + [{port, 8080}], + [{env, [{dispatch, Dispatch}]}] +). +``` + +Cowboy features many kinds of handlers. For this simple example, +we will just use the plain HTTP handler, which has three callback +functions: init/3, handle/2 and terminate/3. You can find more information +about the arguments and possible return values of these callbacks in the +[cowboy_http_handler function reference](http://ninenines.eu/docs/en/cowboy/HEAD/manual/cowboy_http_handler). +Following is an example of a simple HTTP handler module. + +``` erlang +-module(my_handler). +-behaviour(cowboy_http_handler). + +-export([init/3]). +-export([handle/2]). +-export([terminate/3]). + +init({tcp, http}, Req, Opts) -> + {ok, Req, undefined_state}. + +handle(Req, State) -> + {ok, Req2} = cowboy_req:reply(200, [], <<"Hello World!">>, Req), + {ok, Req2, State}. + +terminate(Reason, Req, State) -> + ok. +``` + +The `Req` variable above is the Req object, which allows the developer +to obtain information about the request and to perform a reply. Its usage +is explained in the [cowboy_req function reference](http://ninenines.eu/docs/en/cowboy/HEAD/manual/cowboy_req). + +You can find many examples in the `examples/` directory of the +Cowboy repository. A more complete "Hello world" example can be +found in the `examples/hello_world/` directory. |