minimal-ws-broker
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@ -3,3 +3,70 @@
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server|Minimal examples providing a server
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client|Minimal examples providing a client
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client-server|Minimal examples providing client and server connections simultaneously
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## FAQ
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### What should I look at first
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server/minimal-http-server
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### Why are most of the sources split into a main C file file and a protocol file?
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Lws supports three ways to implement the protocol callback code:
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- you can just add it all in the same source file
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- you can separate it as these examples do, and #include it
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into the main sources
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- you can build it as a standalone plugin that is discovered
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and loaded at runtime.
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The way these examples are structured, you can easily also build
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the protocol callback as a plugin just with a different
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CMakeLists.txt... see https://github.com/warmcat/libwebsockets/tree/master/plugin-standalone
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for an example.
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### Why would we want the protocol as a plugin?
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You will notice a lot of the main C code is the same boilerplate
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repeated for each example. The actual interesting part is in
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the protocol callback only.
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Lws provides a generic lightweight server app called 'lwsws' that
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can be configured by JSON. Combined with your protocol as a plugin,
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it means you don't actually have to make a special server "app"
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part, you can just use lwsws and pass per-vhost configuration
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from JSON into your protocol. (Of course in some cases you have
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an existing app you are bolting lws on to, then you don't care
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about this for that particular case).
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Because lwsws has no dependency on whatever your plugin does, it
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can mix and match different protocols without needing any code
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changes. It reduces the size of the task to just writing the
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code you care about in your protocol handler.
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### I get why there is a pss, but why is there a vhd?
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The pss is instantiated per-connection. But there are almost always
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other variables that have a lifetime longer than a single connection.
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You could make these variables "filescope" one-time globals, but that
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means your protocol cannot instantiate multiple times.
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Lws supports vhosts (virtual hosts), for example both https://warmcat.com
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and https://libwebsockets are running on the same lwsws instance on the
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same server and same IP... each of these is a separate vhost.
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Your protocol may be enabled on multiple vhosts, each of these vhosts
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provides a different vhd specific to the protocol instance on that
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vhost. For example many of the samples keep a linked-list head to
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a list of live pss in the vhd... that means it's cleanly a list of
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pss opened **on that vhost**. If another vhost has the protocol
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enabled, connections to that will point to a different vhd.
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The example "server/minimal-ws-server-threads" demonstrates how to deliver
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external configuration data to a specific vhost + protocol
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combination using code. In lwsws, this is simply a matter of setting
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the desired JSON config.
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@ -7,4 +7,4 @@ minimal-ws-server-pmd|Simple ws server with permessage-deflate support
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minimal-ws-server-pmd-bulk|Simple ws server showing how to pass bulk data with permessage-deflate
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minimal-ws-server-ring|Like minimal-ws-server but holds the chat in a multi-tail ringbuffer
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minimal-ws-server-threads|Simple ws server where data is produced by different threads
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minimal-ws-broker|Simple ws server with a publish / broker / subscribe architecture
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11
minimal-examples/server/minimal-ws-broker/CMakeLists.txt
Normal file
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minimal-examples/server/minimal-ws-broker/CMakeLists.txt
Normal file
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cmake_minimum_required(VERSION 2.8)
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set(SAMP lws-minimal-ws-broker)
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set(SRCS minimal-ws-broker.c)
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if (UNIX)
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set(CMAKE_C_FLAGS "-Wall -Wsign-compare -Wignored-qualifiers -Wtype-limits -Wuninitialized -Werror -Wundef ${CMAKE_C_FLAGS}" )
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endif()
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add_executable(${SAMP} ${SRCS})
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target_link_libraries(${SAMP} -lwebsockets)
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26
minimal-examples/server/minimal-ws-broker/README.md
Normal file
26
minimal-examples/server/minimal-ws-broker/README.md
Normal file
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# lws minimal ws broker
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## build
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```
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$ cmake . && make
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```
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## usage
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```
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$ ./lws-minimal-ws-broker
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[2018/03/15 12:23:12:1559] USER: LWS minimal ws broker | visit http://localhost:7681
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[2018/03/15 12:23:12:1560] NOTICE: Creating Vhost 'default' port 7681, 2 protocols, IPv6 off
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```
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Visit http://localhost:7681 on multiple browser windows
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The page opens a subscribe mode ws connection back to the broker,
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and a publisher mode ws connection back to the broker.
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The textarea shows the data from the subscription connection.
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If you type text is in the text box and press send, the text
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is passed to the broker on the publisher ws connection and
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sent to all subscribers.
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/*
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* lws-minimal-ws-broker
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*
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* Copyright (C) 2018 Andy Green <andy@warmcat.com>
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*
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* This file is made available under the Creative Commons CC0 1.0
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* Universal Public Domain Dedication.
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*
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* This demonstrates the most minimal http server you can make with lws,
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* with an added publish / broker / subscribe ws server.
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*
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* To keep it simple, it serves stuff in the subdirectory "./mount-origin" of
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* the directory it was started in.
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* You can change that by changing mount.origin.
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*/
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#include <libwebsockets.h>
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#include <string.h>
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#include <signal.h>
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#define LWS_PLUGIN_STATIC
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#include "protocol_lws_minimal.c"
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static struct lws_protocols protocols[] = {
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{ "http", lws_callback_http_dummy, 0, 0 },
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LWS_PLUGIN_PROTOCOL_MINIMAL,
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{ NULL, NULL, 0, 0 } /* terminator */
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};
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static int interrupted;
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static const struct lws_http_mount mount = {
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/* .mount_next */ NULL, /* linked-list "next" */
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/* .mountpoint */ "/", /* mountpoint URL */
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/* .origin */ "./mount-origin", /* serve from dir */
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/* .def */ "index.html", /* default filename */
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/* .protocol */ NULL,
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/* .cgienv */ NULL,
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/* .extra_mimetypes */ NULL,
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/* .interpret */ NULL,
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/* .cgi_timeout */ 0,
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/* .cache_max_age */ 0,
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/* .auth_mask */ 0,
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/* .cache_reusable */ 0,
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/* .cache_revalidate */ 0,
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/* .cache_intermediaries */ 0,
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/* .origin_protocol */ LWSMPRO_FILE, /* files in a dir */
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/* .mountpoint_len */ 1, /* char count */
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/* .basic_auth_login_file */ NULL,
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};
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void sigint_handler(int sig)
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{
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interrupted = 1;
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}
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int main(int argc, char **argv)
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{
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struct lws_context_creation_info info;
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struct lws_context *context;
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int n = 0;
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signal(SIGINT, sigint_handler);
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memset(&info, 0, sizeof info); /* otherwise uninitialized garbage */
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info.port = 7681;
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info.mounts = &mount;
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info.protocols = protocols;
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lws_set_log_level(LLL_ERR | LLL_WARN | LLL_NOTICE | LLL_USER
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/* | LLL_INFO */ /* | LLL_DEBUG */, NULL);
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lwsl_user("LWS minimal ws broker | visit http://localhost:7681\n");
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context = lws_create_context(&info);
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if (!context) {
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lwsl_err("lws init failed\n");
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return 1;
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}
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while (n >= 0 && !interrupted)
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n = lws_service(context, 1000);
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lws_context_destroy(context);
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return 0;
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}
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<meta charset="UTF-8">
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<html>
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<body>
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<img src="libwebsockets.org-logo.png"><br>
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LWS chat <b>minimal ws broker example</b>.<br>
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This page opens two separate ws connections...<br>
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A subscriber ws connection fills this textarea<br>
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with data it receives from the broker...
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<br>
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<br>
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<textarea id=r readonly cols=40 rows=10></textarea><br>
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<br>
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... and a publisher ws connection sends the string<br>
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in the box below to the broker when you press Send.<br>
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<input type="text" id=m cols=40 rows=1>
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<button id=b onclick="sendmsg();">Send</button>
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</body>
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<script>
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function get_appropriate_ws_url(extra_url)
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{
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var pcol;
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var u = document.URL;
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/*
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* We open the websocket encrypted if this page came on an
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* https:// url itself, otherwise unencrypted
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*/
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if (u.substring(0, 5) == "https") {
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pcol = "wss://";
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u = u.substr(8);
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} else {
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pcol = "ws://";
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if (u.substring(0, 4) == "http")
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u = u.substr(7);
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}
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u = u.split('/');
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/* + "/xxx" bit is for IE10 workaround */
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return pcol + u[0] + "/" + extra_url;
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}
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function new_ws(urlpath, protocol)
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{
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if (typeof MozWebSocket != "undefined")
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return new MozWebSocket(urlpath, protocol);
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return new WebSocket(urlpath, protocol);
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}
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subscriber_ws = new_ws(get_appropriate_ws_url(""), "lws-minimal-broker");
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try {
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subscriber_ws.onopen = function() {
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document.getElementById("b").disabled = 0;
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}
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subscriber_ws.onmessage =function got_packet(msg) {
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document.getElementById("r").value =
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document.getElementById("r").value + msg.data + "\n";
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document.getElementById("r").scrollTop =
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document.getElementById("r").scrollHeight;
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}
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subscriber_ws.onclose = function(){
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document.getElementById("b").disabled = 1;
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}
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} catch(exception) {
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alert('<p>Error' + exception);
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}
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publisher_ws = new_ws(get_appropriate_ws_url("/publisher"), "lws-minimal-broker");
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try {
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publisher_ws.onopen = function() {
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document.getElementById("m").disabled = 0;
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}
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publisher_ws.onmessage =function got_packet(msg) {
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}
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publisher_ws.onclose = function(){
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document.getElementById("m").disabled = 1;
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}
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} catch(exception) {
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alert('<p>Error' + exception);
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}
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function sendmsg()
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{
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publisher_ws.send(document.getElementById("m").value);
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document.getElementById("m").value = "";
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}
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</script>
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</html>
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258
minimal-examples/server/minimal-ws-broker/protocol_lws_minimal.c
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258
minimal-examples/server/minimal-ws-broker/protocol_lws_minimal.c
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/*
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* ws protocol handler plugin for "lws-minimal-broker"
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*
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* Copyright (C) 2010-2018 Andy Green <andy@warmcat.com>
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*
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* This file is made available under the Creative Commons CC0 1.0
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* Universal Public Domain Dedication.
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*
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* This implements a minimal "broker", for systems that look like this
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*
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* [ publisher ws client ] <-> [ ws server broker ws server ] <-> [ ws client subscriber ]
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*
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* The "publisher" role is to add data to the broker.
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*
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* The "subscriber" role is to hear about all data added to the system.
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*
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* The "broker" role is to manage incoming data from publishers and pass it out
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* to subscribers.
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*
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* Any number of publishers and subscribers are supported.
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*
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* This example implements a single ws server, using one ws protocol, that treats ws
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* connections as being in publisher or subscriber mode according to the URL the ws
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* connection was made to. ws connections to "/publisher" URL are understood to be
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* publishing data and to any other URL, subscribing.
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*/
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#if !defined (LWS_PLUGIN_STATIC)
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#define LWS_DLL
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#define LWS_INTERNAL
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#include <libwebsockets.h>
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#endif
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#include <string.h>
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/* one of these created for each message */
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struct msg {
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void *payload; /* is malloc'd */
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size_t len;
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};
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/* one of these is created for each client connecting to us */
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struct per_session_data__minimal {
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struct per_session_data__minimal *pss_list;
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struct lws *wsi;
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uint32_t tail;
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char publishing; /* nonzero: peer is publishing to us */
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};
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/* one of these is created for each vhost our protocol is used with */
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struct per_vhost_data__minimal {
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struct lws_context *context;
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struct lws_vhost *vhost;
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const struct lws_protocols *protocol;
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struct per_session_data__minimal *pss_list; /* linked-list of live pss*/
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struct lws_ring *ring; /* ringbuffer holding unsent messages */
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};
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/* destroys the message when everyone has had a copy of it */
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static void
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__minimal_destroy_message(void *_msg)
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{
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struct msg *msg = _msg;
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free(msg->payload);
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msg->payload = NULL;
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msg->len = 0;
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}
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static int
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callback_minimal(struct lws *wsi, enum lws_callback_reasons reason,
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void *user, void *in, size_t len)
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{
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struct per_session_data__minimal *pss =
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(struct per_session_data__minimal *)user;
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struct per_vhost_data__minimal *vhd =
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(struct per_vhost_data__minimal *)
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lws_protocol_vh_priv_get(lws_get_vhost(wsi),
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lws_get_protocol(wsi));
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const struct msg *pmsg;
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struct msg amsg;
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uint32_t oldest;
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char buf[32];
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int n, m;
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switch (reason) {
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case LWS_CALLBACK_PROTOCOL_INIT:
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vhd = lws_protocol_vh_priv_zalloc(lws_get_vhost(wsi),
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lws_get_protocol(wsi),
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sizeof(struct per_vhost_data__minimal));
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vhd->context = lws_get_context(wsi);
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vhd->protocol = lws_get_protocol(wsi);
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vhd->vhost = lws_get_vhost(wsi);
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vhd->ring = lws_ring_create(sizeof(struct msg), 8,
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__minimal_destroy_message);
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break;
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case LWS_CALLBACK_PROTOCOL_DESTROY:
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lws_ring_destroy(vhd->ring);
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break;
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case LWS_CALLBACK_ESTABLISHED:
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/* add ourselves to the list of live pss held in the vhd */
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pss->pss_list = vhd->pss_list;
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vhd->pss_list = pss;
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pss->tail = lws_ring_get_oldest_tail(vhd->ring);
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pss->wsi = wsi;
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if (lws_hdr_copy(wsi, buf, sizeof(buf), WSI_TOKEN_GET_URI) > 0)
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pss->publishing = !strcmp(buf, "/publisher");
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break;
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case LWS_CALLBACK_CLOSED:
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/* remove our closing pss from the list of live pss */
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lws_start_foreach_llp(struct per_session_data__minimal **,
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ppss, vhd->pss_list) {
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if (*ppss == pss) {
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*ppss = pss->pss_list;
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break;
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}
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} lws_end_foreach_llp(ppss, pss_list);
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break;
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case LWS_CALLBACK_SERVER_WRITEABLE:
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if (pss->publishing)
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break;
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pmsg = lws_ring_get_element(vhd->ring, &pss->tail);
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if (!pmsg)
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break;
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/* notice we allowed for LWS_PRE in the payload already */
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m = lws_write(wsi, pmsg->payload + LWS_PRE, pmsg->len,
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LWS_WRITE_TEXT);
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if (m < (int)pmsg->len) {
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lwsl_err("ERROR %d writing to di socket\n", n);
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return -1;
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}
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n = lws_ring_get_oldest_tail(vhd->ring) == pss->tail;
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lws_ring_consume(vhd->ring, &pss->tail, NULL, 1);
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if (n) { /* we may have been the oldest tail */
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n = 0;
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oldest = pss->tail;
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lws_start_foreach_llp(
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struct per_session_data__minimal **,
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ppss, vhd->pss_list) {
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m = lws_ring_get_count_waiting_elements(
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vhd->ring, &(*ppss)->tail);
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if (m > n) {
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n = m;
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oldest = (*ppss)->tail;
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}
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} lws_end_foreach_llp(ppss, pss_list);
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/* this will delete any entries behind the new oldest */
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lws_ring_update_oldest_tail(vhd->ring, oldest);
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}
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||||
/* more to do? */
|
||||
if (lws_ring_get_element(vhd->ring, &pss->tail))
|
||||
/* come back as soon as we can write more */
|
||||
lws_callback_on_writable(pss->wsi);
|
||||
break;
|
||||
|
||||
case LWS_CALLBACK_RECEIVE:
|
||||
|
||||
if (!pss->publishing)
|
||||
break;
|
||||
|
||||
n = (int)lws_ring_get_count_free_elements(vhd->ring);
|
||||
if (!n) {
|
||||
lwsl_user("dropping!\n");
|
||||
break;
|
||||
}
|
||||
|
||||
amsg.len = len;
|
||||
/* notice we over-allocate by LWS_PRE */
|
||||
amsg.payload = malloc(LWS_PRE + len);
|
||||
if (!amsg.payload) {
|
||||
lwsl_user("OOM: dropping\n");
|
||||
break;
|
||||
}
|
||||
|
||||
memcpy((char *)amsg.payload + LWS_PRE, in, len);
|
||||
if (!lws_ring_insert(vhd->ring, &amsg, 1)) {
|
||||
__minimal_destroy_message(&amsg);
|
||||
lwsl_user("dropping!\n");
|
||||
break;
|
||||
}
|
||||
|
||||
/*
|
||||
* let every subscriber know we want to write something
|
||||
* on them as soon as they are ready
|
||||
*/
|
||||
lws_start_foreach_llp(struct per_session_data__minimal **,
|
||||
ppss, vhd->pss_list) {
|
||||
if (!(*ppss)->publishing)
|
||||
lws_callback_on_writable((*ppss)->wsi);
|
||||
} lws_end_foreach_llp(ppss, pss_list);
|
||||
break;
|
||||
|
||||
default:
|
||||
break;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
#define LWS_PLUGIN_PROTOCOL_MINIMAL \
|
||||
{ \
|
||||
"lws-minimal-broker", \
|
||||
callback_minimal, \
|
||||
sizeof(struct per_session_data__minimal), \
|
||||
128, \
|
||||
0, NULL, 0 \
|
||||
}
|
||||
|
||||
#if !defined (LWS_PLUGIN_STATIC)
|
||||
|
||||
/* boilerplate needed if we are built as a dynamic plugin */
|
||||
|
||||
static const struct lws_protocols protocols[] = {
|
||||
LWS_PLUGIN_PROTOCOL_MINIMAL
|
||||
};
|
||||
|
||||
LWS_EXTERN LWS_VISIBLE int
|
||||
init_protocol_minimal(struct lws_context *context,
|
||||
struct lws_plugin_capability *c)
|
||||
{
|
||||
if (c->api_magic != LWS_PLUGIN_API_MAGIC) {
|
||||
lwsl_err("Plugin API %d, library API %d", LWS_PLUGIN_API_MAGIC,
|
||||
c->api_magic);
|
||||
return 1;
|
||||
}
|
||||
|
||||
c->protocols = protocols;
|
||||
c->count_protocols = ARRAY_SIZE(protocols);
|
||||
c->extensions = NULL;
|
||||
c->count_extensions = 0;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
LWS_EXTERN LWS_VISIBLE int
|
||||
destroy_protocol_minimal(struct lws_context *context)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
#endif
|
Loading…
Add table
Reference in a new issue