Httpd and Websocket
简介
本文档对应
components/websockets组件, 该组件移植开源libwebsockets 4.3.3版本 。主要移植和适配了 3 个方面的功：http server,Websocket server,Websocket client， 同时也对HTTPS和WSS功能做了适配。移植
libwebsockets时, 没有修改它的 API ，也没有在其基础上额外封装接口，所以在开发时，除了可以参考本 SDK 中相关 examples 外, 还可以参考libwebsockets原生的 examples 和 API 接口。
libwebsockets
功能列表
配置
websockets 组件有 2 个配置
CONFIG_COMPONENT_WEBSOCKET_ENABLED配置打开 websockets 模块；
CONFIG_WEBSOCKET_SECURITY配置使用安全，打开后 HTTPS, WSS 才能使用。其他模块相关配置：
CONFIG_COMPONENT_LWIP_ENABLED打开 LWIP, 必须打开；
LWIP_ENABLE_IPV6打开后 websockets 模块才能支持 IPV6 功能。
Websocket Client
使用
libwebsockets作为WS client链接服务器，发送数据给 Server 和接收 Server 发过来的程序，通常有创建 Context, 连接 server, 调度和事件处理几个步骤，其中发送和接收数据是在回调事件处理中进行的。创建 Context
下面是创建
websocket client端 context 的过程：/*set protocols information*/ static struct lws_protocols g_protocols[] = { { .name = "echo-protocol", .callback = client_callback, .rx_buffer_size = 1024, .tx_packet_size = 1024, }, LWS_PROTOCOL_LIST_TERM }; int is_ssl_connection = 1; /* set context creation information */ struct lws_context_creation_info info; memset(&info, 0, sizeof info); info.port = CONTEXT_PORT_NO_LISTEN; info.protocols = g_protocols; info.options = (is_ssl_connection ? LWS_SERVER_OPTION_DO_SSL_GLOBAL_INIT : 0); info.gid = -1; info.uid = -1; if (is_ssl_connection) { /*set CA certificate*/ info.client_ssl_ca_mem = g_ca_root_cert; info.client_ssl_ca_mem_len = strlen(g_ca_root_cert) + 1; } /* create libwebsockets context*/ context = lws_create_context(&info); if (!context) { lwsl_err("lws init failed\n"); return WM_ERR_FAILED; }连接 Server
下面是
websocket client连接server端的过程：#define EXAMPLE_ALLOW_SELF_SIGNED 0 struct lws *lws = NULL; struct lws_client_connect_info ccinfo; const char* url_host = "echo.websocket.org"; const char* url_path = "/"; int url_port = 80; memset(&ccinfo, 0, sizeof ccinfo); ccinfo.context = context; ccinfo.address = url_host; ccinfo.port = url_port; ccinfo.path = url_path; ccinfo.host = ccinfo.address; ccinfo.origin = ccinfo.address; ccinfo.protocol = g_protocols[0].name; ccinfo.ssl_connection = (is_ssl_connection ? LCCSCF_USE_SSL : 0); if (is_ssl_connection && EXAMPLE_ALLOW_SELF_SIGNED) { ccinfo.ssl_connection |= (LCCSCF_ALLOW_SELFSIGNED | LCCSCF_SKIP_SERVER_CERT_HOSTNAME_CHECK); } lws = lws_client_connect_via_info(&ccinfo); if (!lws){ wm_log_error("connect fail"); return WM_ERR_FAILED; }调度：
while (!g_done) { lws_service(context, 100); }事件处理
LWS_CALLBACK_CLIENT_ESTABLISHED: 创建 websockets 连接完成，完成后可以开始数据发送；LWS_CALLBACK_CLIENT_RECEIVE: 接收到 Server 数据；LWS_CALLBACK_CLIENT_WRITEABLE: 在该事件中发送数据到 Server ；static int client_callback(struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len) { wm_log_debug("reason=%d", reason); switch (reason) { case LWS_CALLBACK_CLIENT_CONNECTION_ERROR: { wm_log_error("ev=CLIENT_CONNECTION_ERROR: %s", in ? (char *)in : "(null)"); g_done = 1; break; } case LWS_CALLBACK_CLIENT_ESTABLISHED: { /* attach to websocket server ok */ const char *msg = "Hello, server!"; unsigned char buf[LWS_PRE + 1024]; unsigned char *p = &buf[LWS_PRE]; wm_log_info("ev=LWS_CALLBACK_CLIENT_ESTABLISHED"); wm_log_info("send message: \n%s", (char *)msg); memcpy(p, msg, strlen(msg)); /* send msg to websocket server */ if (lws_write(wsi, p, strlen(msg), LWS_WRITE_TEXT) < 0) { wm_log_error("Failed to send data to server"); } break; } case LWS_CALLBACK_CLIENT_WRITEABLE: { break; } case LWS_CALLBACK_CLIENT_RECEIVE: { /* receive msg from websocket server */ wm_log_info("ev=LWS_CALLBACK_RECEIVE"); wm_log_info("Received message: \n%s", (char *)in); break; } case LWS_CALLBACK_CLIENT_CLOSED: { wm_log_info("ev=LWS_CALLBACK_CLIENT_CLOSED"); g_done = 1; break; } default: break; } return 0; }
Webosocket Server
使用
libwebsockets作为WS server, 让 Client 连接进来，发送数据给 Client 和接收来自 Client 发过来的数据，通常有创建 Context, 调度和处理事件几个部分，其中发送和接收数据是在回调事件处理中进行的。创建 Context
下面是创建 websocket server 端 context 的过程：
struct lws_context_creation_info info = { 0 }; struct lws_context *context; static struct lws_protocols protocols[] = { { "echo_server", callback_websocket, 0, EXAMPLE_MAX_RECV_BUF_SIZE, }, LWS_PROTOCOL_LIST_TERM }; memset(&info, 0, sizeof(info)); info.port = CONFIG_EXAMPLE_PORT; //80 or 443 info.protocols = protocols; info.gid = -1; info.uid = -1; #ifdef CONFIG_EXAMPLE_SECURITY info.options = LWS_SERVER_OPTION_DO_SSL_GLOBAL_INIT; info.server_ssl_cert_mem = (unsigned char *)g_cert_mem; info.server_ssl_cert_mem_len = strlen(g_cert_mem); info.server_ssl_private_key_mem = (unsigned char *)g_key_mem; info.server_ssl_private_key_mem_len = strlen(g_key_mem); #endif /* Create the WebSocket context */ context = lws_create_context(&info); if (!context) { wm_log_error("lws context creation failed"); return WM_ERR_FAILED; }调度
while (1) { lws_service(context, 100); }回调事件处理
/* process websocket event */ static int callback_websocket(struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len) { switch (reason) { case LWS_CALLBACK_ESTABLISHED: /* Connected from client */ wm_log_info("Client connected\n"); break; case LWS_CALLBACK_RECEIVE: /* received data from client */ wm_log_info("Received msg from client: \n%.*s", (int)len, (char *)in); lws_write(wsi, in, len, LWS_WRITE_TEXT); wm_log_info("Send msg to client: \n%.*s", (int)len, (char *)in); break; case LWS_CALLBACK_CLIENT_WRITEABLE: break; case LWS_CALLBACK_CLOSED: /* closed by client */ wm_log_info("Client disconnected\n"); break; default: break; } return 0; }
Http Server
使用
libwebsockets作为http server, 让 Client 连接进来，通常有创建 Context, 调度和处理事件几个部分，其中发送和接收数据是在回调事件处理中进行的。创建 context 和调度部分和 websocket server类似。回调事件事件处理有一些差异。回调事件处理
LWS_CALLBACK_HTTP: 参数 in 是请求路径，len是路径长度LWS_CALLBACK_HTTP_BODY: 参数 in 是收到 Client 请求的消息提，不包括HTTP header部分LWS_CALLBACK_HTTP_BODY_COMPLETION： body 接收完成事件static int callback_http(struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len) { switch (reason) { case LWS_CALLBACK_HTTP: { /*receive http header*/ wm_log_info("LWS_CALLBACK_HTTP"); wm_log_info("path:%s", (char *)in); return 0; } case LWS_CALLBACK_HTTP_BODY: { /*receive http body*/ wm_log_info("LWS_CALLBACK_HTTP_BODY"); if (in) { wm_log_info("recv body=\n%.*s", len, (char *)in); return 0; } break; } case LWS_CALLBACK_HTTP_BODY_COMPLETION: { /*receive http body end*/ const char *response_json = "{\"status\": \"success\", \"message\": \"Received your request.\"}"; unsigned char buf[LWS_PRE + 256]; unsigned char *p = &buf[LWS_PRE]; int n; wm_log_info("LWS_CALLBACK_HTTP_BODY_COMPLETION"); n = sprintf((char *)p, "HTTP/1.1 200 OK\r\n" "Content-Type: application/json\r\n" "Content-Length: %u\r\n" "Connection: close\r\n" "\r\n" "%s", strlen(response_json), response_json); /*write response to http client*/ lws_write(wsi, p, n, LWS_WRITE_HTTP); wm_log_info("response=\n%s", response_json); break; } default: break; } return lws_callback_http_dummy(wsi, reason, user, in, len); }备注
使用
libwebsockets创建 http Server，因缺少VFS, 暂时不支持文件服务部分，参考示例中只支持 post, get 数据请求服务。备注
使用
libwebsockets创建 http Server 或者 Websockets server 时，支持的 Client 数量大概是 3 ~ 5 个，原因是 LWIP 连接数量限制，增大 lwipopts.h 文件中的 MEMP_NUM_NETCONN 宏可以支持更多。
应用实例
使用 websocket 基本示例请参照 examples/network 其中：
websocket client: 示例请参照 examples/network/websocket/websocket_client/
websocket server: 示例请参照 examples/network/websocket/websocket_server/
http server: 示例请参照 examples/network/httpd/http_server_post/