= ranch:handshake(3)

== Name

ranch:handshake - Perform the transport handshake

== Description

[source,erlang]
----
handshake(Ref)       -> handshake(Ref, [])
handshake(Ref, Opts) -> {ok, Socket}

Ref    :: ranch:ref()
Opts   :: any()
Socket :: any()
----

Perform the transport handshake.

This function must be called by the protocol process in order
to retrieve the socket for the connection. Ranch performs the
handshake necessary to give control of the socket to this
process and also does the transport handshake, for example
setting up the TLS connection.

Currently the socket can be obtained from a
`Protocol:start_link/4` argument and as a return value
from `ranch:handshake/1,2`. In Ranch 2.0 the socket will
only be available from `ranch:handshake/1,2`.

== Arguments

Ref::

The listener name.

Opts::

Transport handshake options.
+
Allowed options depend on the transport module.

== Return value

An `ok` tuple is returned containing the socket for the connection.

This function will trigger an exception when an error occurs.

== Changelog

* *1.6*: Function introduced. Replaces `ranch:accept_ack/1`.

== Examples

.Initialize the connection process
[source,erlang]
----
start_link(Ref, _, Transport, Opts) ->
    Pid = proc_lib:spawn_link(?MODULE, init,
        [Ref, Transport, Opts]),
    {ok, Pid}.

init(Ref, Transport, Opts) ->
    {ok, Socket} = ranch:handshake(Ref),
    loop(#state{ref=Ref, socket=Socket,
        transport=Transport, opts=Opts}).
----

== See also

link:man:ranch:start_listener(3)[ranch:start_listener(3)],
link:man:ranch:recv_proxy_header(3)[ranch:recv_proxy_header(3)],
link:man:ranch:remove_connection(3)[ranch:remove_connection(3)],
link:man:ranch(3)[ranch(3)]