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Net-Libwebsockets-0.02
River stage zero No dependents
2 ++
/ Net::Libwebsockets

NAME

Net::Libwebsockets - libwebsockets in Perl

SYNOPSIS

WebSocket with AnyEvent (IO::Async is supported, too):

    my $cv = AE::cv();

    my $done_p = Net::Libwebsockets::WebSocket::Client::connect(
        url   => 'wss://echo.websocket.org',
        event => 'AnyEvent',
        on_ready => sub ($courier) {

            # $courier ferries messages between the caller and the peer:

            $courier->send_text( $characters );
            $courier->send_binary( $bytes );

            # If a message arrives for a type that has no listener,
            # a warning is thrown.
            $courier->on_text( sub ($characters) { .. } );
            $courier->on_binary( sub ($bytes) { .. } );
        },
    );

    # This promise finishes when the connection is done.
    # On successful close it resolves with [ $code, $reason ];
    # see the documentation for failure-case behavior.
    #
    $done_p->then(
        sub ($status_reason_ar) { say 'WebSocket finished OK' },
        sub ($err) {
            warn "WebSocket non-success: $err";
        },
    )->finally($cv);

Look at Net::Libwebsockets::WebSocket::Client for documentation of the above.

DESCRIPTION

This module provides a Perl binding to libwebsockets (aka “LWS”), a C library that provides client and server implementations of WebSocket and HTTP/2, among other protocols.

STATUS

This module currently only implements WebSocket, and only as a client. (cf. Net::Libwebsockets::WebSocket::Client) This is all EXPERIMENTAL, so all interfaces are subject to change, and any part of it can blow up in any way at any time.

That said, it’s been in development for some time, and it should be useful enough to play with. Error reporting and memory-leak detection have received especial care. LWS itself is used on tens of millions of devices, so any issues you encounter will likely be solvable readily by fixing this little module rather than delving into LWS.

Note the following:

  • LWS version 4.3.0 or later is required. (As of this writing that’s the latest release.)

  • Some LWS builds lack useful stuff like WebSocket compression or non-blocking DNS queries. If in doubt, check your build.

BUILDING

This module, as of this writing, needs a newer LWS build than most OSes provide. To use Net::Libwebsockets, then, you may need to build your own LWS, then link this module against that build. To simplify that, you can define a LWS_BUILD_DIR environment variable when you run this module’s provided Makefile.PL script. LWS_BUILD_DIR tells Makefile.PL where to find your custom LWS build, which avoids the need to install your custom build globally.

As of this writing LWS’s upstream main branch includes several useful fixes & improvements beyond what the latest release provides. It is thus recommended to build from that branch.

EVENT LOOP SUPPORT

This module supports most of Perl’s popular event loops via either IO::Async or AnyEvent.

LOGGING

LWS historically configured its logging globally; i.e., all LWS contexts within a process shared the same logging configuration.

LWS 4.3.0 introduced context-specific logging alongside the old global-state functions. As of this writing, though, most of LWS’s internal logger calls still use the older functions, which means those log statements will go out however the global logging is configured, regardless of whether there’s a context-specific logging configuration for a given action. Conversion of existing log statements is ongoing.

This library supports both LWS’s old/global and new/contextual logging. See Net::Libwebsockets::Logger and set_log_level() below for more details.

ERRORS

Most of this module’s error classes extend X::Tiny::Base. Errors that are more likely to be programmer misuse than runtime failure are more apt to be simple strings.

MEMORY LEAK DETECTION

Most objects here emit a warning if their DESTROY() method runs at global-destruction time. This usually means either you stored such an object in a global, or you have a memory leak. To silence the warning in the former case, just clear your global at END time. In the latter case, fix your code. :)

SEE ALSO

Other CPAN WebSocket implementations include:

CONSTANTS

This package exposes the following constants. For their meanings see LWS’s documentation.

  • HAS_PMD - A boolean that indicates whether WebSocket compression (i.e., per-message deflate, or PMD) is available.

  • Log levels: LLL_ERR et al. (See here for the others.)

  • TLS/SSL-related: LCCSCF_ALLOW_SELFSIGNED, LCCSCF_SKIP_SERVER_CERT_HOSTNAME_CHECK, LCCSCF_ALLOW_EXPIRED, LCCSCF_ALLOW_INSECURE

FUNCTIONS

Most of this distribution’s controls lie in submodules; however, the present package does expose some functionality of its own:

set_log_level( $LEVEL )

Sets LWS’s global log level, which is the bitwise-OR of the log-level constants referenced above. For example, to see only errors and warnings you can do:

    Net::Libwebsockets::set_log_level(
        Net::Libwebsockets::LLL_ERR | Net::Libwebsockets::LLL_WARN
    );

LWS allows setting a callback to direct log output to someplace other than STDERR. This library, though, does not (currently?) support that except via contextual logging (Net::Libwebsockets::Logger).