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Felipe Gasper
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Net::WebSocket - WebSocket in Perl


    my $handshake = Net::WebSocket::Handshake::Client->new(
        uri => $uri,

    syswrite $inet, $handshake->create_header_text() . "\x0d\x0a" or die $!;

    #You can parse HTTP headers however you want;
    #Net::WebSocket makes no assumptions about this.
    my $req = HTTP::Response->parse($hdrs_txt);

    #XXX More is required for the handshake validation in production!
    my $accept = $req->header('Sec-WebSocket-Accept');

    #See below about IO::Framed
    my $parser = Net::WebSocket::Parser->new(
        $leftover_from_header_read,     #can be nonempty on the client

    my $iof_w = IO::Framed::Write->new($inet);

    my $ept = Net::WebSocket::Endpoint::Client->new(
        parser => $parser,
        out => $iof_w,

        Net::WebSocket::Frame::text->new( payload_sr => \'Hello, world' )

    #Determine that $inet can be read from …

    my $msg = $ept->get_next_message();

    #… or, if we timeout while waiting for $inet to be ready for reading:

    exit if $ept->is_closed();


This is a beta release. It should be safe for production, but there could still be small changes to the API. Please check the changelog before upgrading.


This distribution provides a set of fundamental tools for communicating via WebSocket. It is only concerned with the protocol itself; the underlying transport mechanism is up to you: it could be a file, a UNIX socket, ordinary TCP/IP, some funky tie()d object, or whatever.

Net::WebSocket also “has no opinions” about how you should do I/O or HTTP headers. As a result of this “bare-bones” approach, Net::WebSocket can likely fit your project; however, it won’t absolve you of the need to know some things aboutthe WebSocket protocol itself. There are some examples of how you might write complete applications (client or server) in the distribution’s demo/ directory.

Net::WebSocket is not a “quick” WebSocket solution; for that, check out Mojolicious. Net::WebSocket’s purpose is to support anything that the WebSocket protocol itself can do, as lightly as possible and without prejudice as to how you want to do it: extensions, blocking/non-blocking I/O, arbitrary HTTP headers, etc. Net::WebSocket will likely require more of an investment up-front, but its flexibility should allow it to do anything that can be done with WebSocket, and much more cleanly than a more “monolithic” solution would likely allow.


Here are the main modules:


Logic for handshakes. These are probably most useful in tandem with modules like HTTP::Request and HTTP::Response.


The highest-level abstraction that this distribution provides. It parses input and responds to control frames and timeouts. You can use this to receive streamed (i.e., fragmented) transmissions as well.


Useful for sending streamed (fragmented) data rather than a full message in a single frame.


Translate WebSocket frames out of a filehandle into useful data for your application.


Useful for creating raw frames. For data frames (besides continuation), these will be your bread-and-butter. See Net::WebSocket::Frame::text for sample usage.



WebSocket uses regular HTTP headers for its handshakes. Because there are many different solutions around for parsing HTTP headers, Net::WebSocket tries to be “agnostic” about how that’s done. The liability of this is that you, the library user, will need to implement some of the handshake logic yourself. If you’re building from the ground up that’s not a lot of fun, but if you’ve already got a solution in place for parsing headers then Net::WebSocket can fit into that quite easily.


As per the specification, client serializers “MUST” mask the data randomly, whereas server serializers “MUST NOT” do this. Net::WebSocket does this for you automatically, but you need to distinguish between client serializers—which mask their payloads—and server serializers, which don’t mask.

This module used to do this with Bytes::Random::Secure::Tiny, but that seems like overkill given that the masking is only there to accommodate peculiarities of certain proxies. We now just use Perl’s rand() built-in.

(You should probably use TLS if cryptographically secure masking is something you actually care about?)

Text vs. Binary

Recall that in some languages—like JavaScript!—the difference between “text” and “binary” is much more significant than for us in Perl.

Use of IO::Framed

CPAN’s IO::Framed provides a straightforward interface for chunking up data from byte streams into frames. You don’t have to use it (which is why it’s not listed as a requirement), but you’ll need to provide an equivalent interface if you don’t.


The WebSocket specification describes several methods of extending the protocol, all of which Net::WebSocket supports:

  • The three reserved bits in each frame’s header. (See Net::WebSocket::Frame.) This is used, e.g., in the https://tools.ietf.org/html/rfc7692.

  • Additional opcodes: 3-7 and 11-15. You’ll need to subclass Net::WebSocket::Frame for this, and you will likely want to subclass Net::WebSocket::Parser. If you’re using the custom classes for streaming, then you can also subclass Net::WebSocket::Streamer. See each of those modules for more information on doing this.

    THIS IS NOT WELL TESTED. Proceed with caution, and please file bug reports as needed. (I personally don’t know of any applications that actually use this.)

  • Apportion part of the payload data for the extension. This you can do in your application.


  • Add tests, especially for extension support.


Mojolicious is probably CPAN’s easiest WebSocket implementation to get a server up and running. If you’re building a project from scratch, you may find this to be a better fit for you than Net::WebSocket.

Protocol::WebSocket is an older module that supports pre-standard versions of the WebSocket protocol. It’s similar to this one in that it gives you just the protocol itself, but it doesn’t give you things like automatic ping/pong/close, classes for each message type, etc.

Net::WebSocket::Server implements only server behaviors and gives you more automation than P::WS.

Net::WebSocket::EV uses XS to call a C library.




Felipe Gasper (FELIPE)


Copyright 2017 by Gasper Software Consulting, LLC


This distribution is released under the same license as Perl.

1 POD Error

The following errors were encountered while parsing the POD:

Around line 173:

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