绿色记忆:基于C/C++的WebSocket库

基于C/C++的WebSocket库

By Alex

/ in C,C++,Network

/ tags WebSocket

5 Comments

libwebsockets

简介

libwebsockets是一个纯C语言的轻量级WebSocket库，它的CPU、内存占用很小，同时支持作为服务器端/客户端。其特性包括：

支持ws://和wss://协议
可以选择和OpenSSL、CyaSSL或者WolfSSL链接
轻量和高速，即使在每个线程处理多达250个连接的情况下
支持事件循环、零拷贝。支持poll()、libev（epoll）、libuv

libwebsockets提供的API相当底层，实现简单的功能也需要相当冗长的代码。

构建

git clone git clone https://github.com/warmcat/libwebsockets.git

cd libwebsockets

mkdir build && cd build

cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=/home/alex/CPP/lib/libwebsockets ..

make && make install

Echo示例

CMake项目配置

cmake_minimum_required(VERSION 2.8.9)

project(libws-study C)

include_directories(/home/alex/CPP/lib/libwebsockets/include)

set(CMAKE_CXX_FLAGS "-w -pthread")

set(SF_CLIENT client.c)

set(SF_SERVER server.c)

add_executable(client ${SF_CLIENT})

target_link_libraries(client /home/alex/CPP/lib/libwebsockets/lib/libwebsockets.so)

add_executable(server ${SF_SERVER})

target_link_libraries(server /home/alex/CPP/lib/libwebsockets/lib/libwebsockets.so)

客户端

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#include "libwebsockets.h"

#include <signal.h>

static volatile int exit_sig = 0;

#define MAX_PAYLOAD_SIZE 10 * 1024

void sighdl( int sig ) {

lwsl_notice( "%d traped", sig );

exit_sig = 1;

}

/**

* 会话上下文对象，结构根据需要自定义

struct session_data {

int msg_count;

unsigned char buf[LWS_PRE + MAX_PAYLOAD_SIZE];

int len;

};

/**

* 某个协议下的连接发生事件时，执行的回调函数

* wsi：指向WebSocket实例的指针

* reason：导致回调的事件

* user 库为每个WebSocket会话分配的内存空间

* in 某些事件使用此参数，作为传入数据的指针

* len 某些事件使用此参数，说明传入数据的长度

int callback( struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len ) {

struct session_data *data = (struct session_data *) user;

switch ( reason ) {

case LWS_CALLBACK_CLIENT_ESTABLISHED: // 连接到服务器后的回调

lwsl_notice( "Connected to server\n" );

break;

case LWS_CALLBACK_CLIENT_RECEIVE: // 接收到服务器数据后的回调，数据为in，其长度为len

lwsl_notice( "Rx: %s\n", (char *) in );

break;

case LWS_CALLBACK_CLIENT_WRITEABLE: // 当此客户端可以发送数据时的回调

if ( data->msg_count < 3 ) {

// 前面LWS_PRE个字节必须留给LWS

memset( data->buf, 0, sizeof( data->buf ));

char *msg = (char *) &data->buf[ LWS_PRE ];

data->len = sprintf( msg, "你好 %d", ++data->msg_count );

lwsl_notice( "Tx: %s\n", msg );

// 通过WebSocket发送文本消息

lws_write( wsi, &data->buf[ LWS_PRE ], data->len, LWS_WRITE_TEXT );

}

break;

}

return 0;

}

/**

* 支持的WebSocket子协议数组

* 子协议即JavaScript客户端WebSocket(url, protocols)第2参数数组的元素

* 你需要为每种协议提供回调函数

struct lws_protocols protocols[] = {

{

//协议名称，协议回调，接收缓冲区大小

"", callback, sizeof( struct session_data ), MAX_PAYLOAD_SIZE,

{

NULL, NULL, 0 // 最后一个元素固定为此格式

}

};

int main() {

// 信号处理函数

signal( SIGTERM, sighdl );

// 用于创建vhost或者context的参数

struct lws_context_creation_info ctx_info = { 0 };

ctx_info.port = CONTEXT_PORT_NO_LISTEN;

ctx_info.iface = NULL;

ctx_info.protocols = protocols;

ctx_info.gid = -1;

ctx_info.uid = -1;

// 创建一个WebSocket处理器

struct lws_context *context = lws_create_context( &ctx_info );

char *address = "192.168.0.89";

int port = 9090;

char addr_port[256] = { 0 };

sprintf( addr_port, "%s:%u", address, port & 65535 );

// 客户端连接参数

struct lws_client_connect_info conn_info = { 0 };

conn_info.context = context;

conn_info.address = address;

conn_info.port = port;

conn_info.ssl_connection = 0;

conn_info.path = "/h264src";

conn_info.host = addr_port;

conn_info.origin = addr_port;

conn_info.protocol = protocols[ 0 ].name;

// 下面的调用触发LWS_CALLBACK_PROTOCOL_INIT事件

// 创建一个客户端连接

struct lws *wsi = lws_client_connect_via_info( &conn_info );

while ( !exit_sig ) {

// 执行一次事件循环（Poll），最长等待1000毫秒

lws_service( context, 1000 );

/**

* 下面的调用的意义是：当连接可以接受新数据时，触发一次WRITEABLE事件回调

* 当连接正在后台发送数据时，它不能接受新的数据写入请求，所有WRITEABLE事件回调不会执行

lws_callback_on_writable( wsi );

}

// 销毁上下文对象

lws_context_destroy( context );

return 0;

}

服务器

static int protocol0_callback( struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len ) {

struct session_data *data = (struct session_data *) user;

switch ( reason ) {

case LWS_CALLBACK_ESTABLISHED: // 当服务器和客户端完成握手后

break;

case LWS_CALLBACK_RECEIVE: // 当接收到客户端发来的帧以后

// 判断是否最后一帧

data->fin = lws_is_final_fragment( wsi );

// 判断是否二进制消息

data->bin = lws_frame_is_binary( wsi );

// 对服务器的接收端进行流量控制，如果来不及处理，可以控制之

// 下面的调用禁止在此连接上接收数据

lws_rx_flow_control( wsi, 0 );

// 业务处理部分，为了实现Echo服务器，把客户端数据保存起来

memcpy( &data->buf[ LWS_PRE ], in, len );

data->len = len;

// 需要给客户端应答时，触发一次写回调

lws_callback_on_writable( wsi );

break;

case LWS_CALLBACK_SERVER_WRITEABLE: // 当此连接可写时

lws_write( wsi, &data->buf[ LWS_PRE ], data->len, LWS_WRITE_TEXT );

// 下面的调用允许在此连接上接收数据

lws_rx_flow_control( wsi, 1 );

break;

}

// 回调函数最终要返回0，否则无法创建服务器

return 0;

}

int main() {

// 信号处理函数

signal( SIGTERM, sighdl );

struct lws_context_creation_info ctx_info = { 0 };

ctx_info.port = 9090;

ctx_info.iface = NULL; // 在所有网络接口上监听

ctx_info.protocols = protocols;

ctx_info.gid = -1;

ctx_info.uid = -1;

ctx_info.options = LWS_SERVER_OPTION_VALIDATE_UTF8;

struct lws_context *context = lws_create_context( &ctx_info );

while ( !exit_sig ) {

lws_service( context, 1000 );

}

lws_context_destroy( context );

}

封装

为了简化编程复杂度，应该考虑对libwebsockets进行适当封装。本节给出一个简单封装的例子。

客户端封装

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#ifndef LIVE555_WSCLIENT_H

#define LIVE555_WSCLIENT_H

#include "libwebsockets.h"

#ifndef LWS_MAX_PAYLOAD_SIZE

#define LWS_MAX_PAYLOAD_SIZE 1024 * 1024

#endif

#ifndef SPDLOG_CONST

#define SPDLOG_CONST

const auto LOGGER = spdlog::stdout_color_st( "console" );

#endif

/**

* 通用回调函数签名

typedef void (*lws_callback)( struct lws *wsi, void *user, void *in, size_t len );

// 用户数据对象

typedef struct lws_user_data {

// 缓冲区

unsigned char *buf;

// 缓冲区有效字节数

int len;

// 用户自定义数据

void *user;

// 读写缓冲区之前需要加锁

volatile bool locked;

// 指示当前缓冲区的数据的重要性，如果为真，发送之前不得被覆盖

volatile bool critical;

// 本次数据发送类型

lws_write_protocol type;

// 回调函数

lws_callback esta_callback;

lws_callback recv_callback;

lws_callback writ_callback;

};

void writ_callback_send_buf( struct lws *wsi, void *user, void *in, size_t len ) {

struct lws_user_data *data = (struct lws_user_data *) user;

if ( __sync_bool_compare_and_swap( &data->locked, 0, 1 )) {

unsigned char *buf;

char hex[128]= { 0 };

int writ_count;

int len = data->len;

if ( len == 0 ) goto cleanup;

buf = data->buf + LWS_PRE;

writ_count = lws_write( wsi, buf, len, data->type );

if ( data->type == LWS_WRITE_BINARY ) {

char *phex = hex;

for ( int i = 0; i < 16; i++ ) {

unsigned char c = *buf++;

sprintf( phex, "%02x ", c );

phex += 3;

}

LOGGER->debug( "lws_write {} bytes: {}...", writ_count, hex );

cleanup:

data->locked = 0;

data->critical = 0;

data->len = 0;

}

static int lws_protocol_0_callback( struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len ) {

struct lws_user_data *data = (struct lws_user_data *) user;

switch ( reason ) {

case LWS_CALLBACK_CLIENT_ESTABLISHED:

if ( data->esta_callback )data->esta_callback( wsi, user, in, len );

break;

case LWS_CALLBACK_CLIENT_RECEIVE:

if ( data->recv_callback )data->recv_callback( wsi, user, in, len );

break;

case LWS_CALLBACK_CLIENT_WRITEABLE:

if ( data->writ_callback )data->writ_callback( wsi, user, in, len );

break;

}

return 0;

}

typedef struct lws_client {

struct lws *wsi;

struct lws_context *context;

lws_user_data *data;

int *cycle;

// 连接参数

char *address;

char *path;

int port;

void (*fill_buf)( lws_client *client, void *buf, int len, lws_write_protocol type );

void (*fire_writable)( lws_client *client );

};

void fill_buf( lws_client *client, void *buf, int len, lws_write_protocol type ) {

lws_user_data *data = client->data;

data->type = type;

data->len = len;

memcpy( data->buf + LWS_PRE, buf, len );

}

void fire_writable( lws_client *client ) {

lws_callback_on_writable( client->wsi );

// 停止当前事件循环等待

lws_cancel_service( client->context );

}

void *lws_service_thread_func( void *arg ) {

lws_client *client = (lws_client *) arg;

struct lws_context_creation_info ctx_info = { 0 };

ctx_info.port = CONTEXT_PORT_NO_LISTEN;

ctx_info.iface = NULL;

const struct lws_protocols protocols[] = {

{

"", lws_protocol_0_callback, sizeof( struct lws_user_data ), LWS_MAX_PAYLOAD_SIZE, 0, 0, LWS_MAX_PAYLOAD_SIZE

{

NULL, NULL, 0

}

};

static const struct lws_extension exts[] = {

{

"permessage-deflate",

lws_extension_callback_pm_deflate,

"permessage-deflate; client_no_context_takeover; client_max_window_bits"

{ NULL, NULL, NULL /* terminator */ }

};

ctx_info.protocols = protocols;

ctx_info.extensions = exts;

ctx_info.options = LWS_SERVER_OPTION_VALIDATE_UTF8;

ctx_info.gid = -1;

ctx_info.uid = -1;

struct lws_context *context = lws_create_context( &ctx_info );

client->context = context;

char addr_port[256] = { 0 };

sprintf( addr_port, "%s:%u", client->address, client->port & 65535 );

struct lws_client_connect_info conn_info = { 0 };

conn_info.context = context;

conn_info.address = client->address;

conn_info.port = client->port;

conn_info.ssl_connection = 0;

conn_info.path = client->path;

conn_info.host = addr_port;

conn_info.origin = addr_port;

conn_info.protocol = protocols[ 0 ].name;

// 用户数据对象由调用者提供，因为需要提供回调

conn_info.userdata = client->data;

struct lws *wsi = lws_client_connect_via_info( &conn_info );

client->wsi = wsi;

int *loop_cycle = client->cycle;

int cycle = *loop_cycle;

while ( *loop_cycle >= 0 ) {

lws_service( context, cycle );

}

lws_context_destroy( context );

}

/**

* 连接到WebSocket服务器

* @param address IP地址

* @param path 上下文路径URL

* @param port 端口

* @param data 用户数据

* @param loop_cycle 事件循环周期，如果大于等于0则启动事件循环，后续将其置为-1则导致循环终止

* @return

lws_client *lws_connect( char *address, char *path, int port, lws_user_data *data, int loop_cycle ) {

lws_client *client = (lws_client *) malloc( sizeof( lws_client ));

client->data = data;

client->cycle = (int *) malloc( sizeof( int ));

*client->cycle = loop_cycle;

client->address = address;

client->path = path;

client->port = port;

client->fill_buf = fill_buf;

client->fire_writable = fire_writable;

pthread_t *lws_service_thread = (pthread_t *) malloc( sizeof( pthread_t ));

pthread_create( lws_service_thread, NULL, lws_service_thread_func, client );

return client;

}

#endif

使用客户端封装

// 创建用户数据对象

lws_user_data *data = new lws_user_data();

data->buf = new unsigned char[LWS_PRE + LWS_MAX_PAYLOAD_SIZE];

data->writ_callback = writ_callback_send_buf_bin; // 注册回调

// 创建客户端

lws_client *ws_client = lws_connect( "192.168.0.89", "/h264src", 9090, data, 10 );

// 发送数据，需要同步

lws_user_data *data = client->data;

// GCC内置CAS语义

if ( __sync_bool_compare_and_swap( &data->locked, 0, 1 )) {

client->fill_buf( client, sink->recvBuf, frameSize );

client->fire_writable( client );

data->locked = 0;

}

常见问题

error on reading from skt : 104

错误代码104的含义是连接被重置，我遇到这个问题的原因是，Spring的WebSocket消息缓冲区大小不足。

WebSocket++

简介

WebSocket++是一个仅仅由头文件构成的C++库，它实现了WebSocket协议（RFC6455），通过它，你可以在C++项目中使用WebSocket客户端或者服务器。

WebSocket++使用两个可以相互替换的网络传输模块，其中一个基于C++ I/O流，另一个基于Asio。

WebSocket++的主要特性包括：

事件驱动的接口
支持WSS、IPv6
灵活的依赖管理 —— Boost或者C++ 11标准库
可移植性：Posix/Windows、32/64bit、Intel/ARM/PPC
线程安全

构建

git clone https://github.com/zaphoyd/websocketpp.git

cd websocketpp

mkdir build && cd build

cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=/home/alex/CPP/lib/websocketpp ..

make && make install

Echo示例

CMake项目配置

cmake_minimum_required(VERSION 3.6)

project(websocket__)

set(CMAKE_CXX_STANDARD 11)

set(CMAKE_CXX_FLAGS "-pthread")

add_definitions(-D_WEBSOCKETPP_CPP11_FUNCTIONAL_)

add_definitions(-D_WEBSOCKETPP_CPP11_THREAD_)

add_definitions(-D_WEBSOCKETPP_CPP11_SYSTEM_ERROR_)

add_definitions(-D_WEBSOCKETPP_CPP11_MEMORY_)

include_directories(/home/alex/CPP/lib/websocketpp/include /home/alex/CPP/lib/boost/1.65.1/include/)

set(SF_CLIENT client.cpp)

add_executable(client ${SF_CLIENT})

target_link_libraries(client /home/alex/CPP/lib/boost/1.65.1/lib/libboost_system.so)

set(SF_SERVER server.cpp)

add_executable(server ${SF_SERVER})

target_link_libraries(server /home/alex/CPP/lib/boost/1.65.1/lib/libboost_system.so)

客户端

#include <websocketpp/config/asio_no_tls_client.hpp>

#include <websocketpp/client.hpp>

#include <iostream>

typedef websocketpp::client<websocketpp::config::asio_client> client;

using websocketpp::lib::placeholders::_1;

using websocketpp::lib::placeholders::_2;

using websocketpp::lib::bind;

// 消息指针

typedef websocketpp::config::asio_client::message_type::ptr message_ptr;

// 打开连接时的回调

void on_open( client *c, websocketpp::connection_hdl hdl ) {

std::string msg = "Hello 1";

// 发送文本消息

c->send( hdl, msg, websocketpp::frame::opcode::text );

c->get_alog().write( websocketpp::log::alevel::app, "Tx: " + msg );

}

// 连接失败时的回调

void on_fail( client *c, websocketpp::connection_hdl hdl ) {

c->get_alog().write( websocketpp::log::alevel::app, "Connection Failed" );

}

// 接收到服务器发来的WebSocket消息后的回调

void on_message( client *c, websocketpp::connection_hdl hdl, message_ptr msg ) {

c->get_alog().write( websocketpp::log::alevel::app, "Rx: " + msg->get_payload());

// 关闭连接，导致事件循环退出

c->close( hdl, websocketpp::close::status::normal, "" );

}

// 关闭连接时的回调

void on_close( client *c, websocketpp::connection_hdl hdl ) {

}

int main( int argc, char *argv[] ) {

client echo_client;

// 调整日志策略

echo_client.clear_access_channels( websocketpp::log::alevel::frame_header );

echo_client.clear_access_channels( websocketpp::log::alevel::frame_payload );

std::string uri = "ws://192.168.0.89:9090/h264src";

try {

// 初始化ASIO ASIO

echo_client.init_asio();

// 注册回调函数

echo_client.set_open_handler( std::bind( &on_open, &echo_client, ::_1 ));

echo_client.set_fail_handler( std::bind( &on_fail, &echo_client, ::_1 ));

echo_client.set_message_handler( std::bind( &on_message, &echo_client, ::_1, ::_2 ));

echo_client.set_close_handler( std::bind( &on_close, &echo_client, ::_1 ));

// 在事件循环启动前创建一个连接对象

websocketpp::lib::error_code ec;

client::connection_ptr con = echo_client.get_connection( uri, ec );

echo_client.connect( con );

con->get_handle(); // 连接句柄，发送消息时必须要传入

// 启动事件循环（ASIO的io_service），当前线程阻塞

echo_client.run();

} catch ( const std::exception &e ) {

std::cout << e.what() << std::endl;

} catch ( websocketpp::lib::error_code e ) {

std::cout << e.message() << std::endl;

} catch ( ... ) {

std::cout << "other exception" << std::endl;

}

服务器

#include <iostream>

#include <websocketpp/config/asio_no_tls.hpp>

#include <websocketpp/server.hpp>

typedef websocketpp::server<websocketpp::config::asio> server;

typedef websocketpp::config::asio::message_type::ptr message_ptr;

using websocketpp::lib::placeholders::_1;

using websocketpp::lib::placeholders::_2;

using websocketpp::lib::bind;

void on_open( server *s, websocketpp::connection_hdl hdl ) {

// 根据连接句柄获得连接对象

server::connection_ptr con = s->get_con_from_hdl( hdl );

// 获得URL路径

std::string path = con->get_resource();

s->get_alog().write( websocketpp::log::alevel::app, "Connected to path " + path );

}

void on_message( server *s, websocketpp::connection_hdl hdl, message_ptr msg ) {

s->send( hdl, msg->get_payload(), websocketpp::frame::opcode::text );

}

int main() {

server echo_server;

// 调整日志策略

echo_server.set_access_channels( websocketpp::log::alevel::all );

echo_server.clear_access_channels( websocketpp::log::alevel::frame_payload );

try {

echo_server.init_asio();

echo_server.set_open_handler( bind( &on_open, &echo_server, ::_1 ));

echo_server.set_message_handler( bind( &on_message, &echo_server, ::_1, ::_2 ));

// 在所有网络接口的9090上监听

echo_server.listen( 9090 );

// 启动服务器端Accept事件循环

echo_server.start_accept();

// 启动事件循环（ASIO的io_service），当前线程阻塞

echo_server.run();

} catch ( websocketpp::exception const &e ) {

std::cout << e.what() << std::endl;

} catch ( ... ) {

std::cout << "other exception" << std::endl;

}

← H.264学习笔记

WebSocket协议 →

5 Comments On This Topic

回复

C++ WebSocket 库 - 算法网

2019/05/23

[…] 基于C/C++的WebSocket库 […]
回复

chengjiaxi

2020/05/21

写的很好，我能转载吗？

回复

Alex

2020/05/21

您可以任意转载、修改:D

回复

吴杰

2021/04/22

你好，请教一下，这里面接收消息的函数怎么设置自动触发么，而不是通过轮训的方式一直调用
回复

C/C++编程：WebSocketpp（Linux + Clion + boostAsio） – 源码巴士

2022/10/06

[…] 这篇博客写的很好，但是我还没有看完 […]

基于C/C++的WebSocket库

基于C/C++的WebSocket库

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