/********************************************************************************** *                libwebsockets libwebsockets-webserver.c hacking * 说明： *     找点libwesockets的资料看看，主要是为后续使用做准备。 * *                                           2017-6-9 深圳 龙华樟坑村 曾剑锋 *********************************************************************************/一、参考文档：    1. libwebsockets如何使用？        https://www.zhihu.com/question/57474416    2. libwebsockets: Simple HTTP server        https://medium.com/@martin.sikora/libwebsockets-simple-http-server-2b34c13ab540    3. martinsik/libwebsockets-webserver.c        https://gist.github.com/martinsik/3216369    4. martinsik/index.html        https://gist.github.com/martinsik/3654228二、代码解读：    #include <stdio.h>    #include <stdlib.h>    #include <string.h>    #include <unistd.h>    #include <libwebsockets.h>            // 浏览器websocket访问的回调函数    static int callback_http(struct libwebsocket_context *context,                             struct libwebsocket *wsi,                             enum libwebsocket_callback_reasons reason, void *user,                             void *in, size_t len)    {                switch (reason) {            // 头文件链接描述，出了作为Server会喷出一行连接建立以外，这里不进行任何处理            // http://git.warmcat.com/cgi-bin/cgit/libwebsockets/tree/lib/libwebsockets.h#n260            case LWS_CALLBACK_CLIENT_WRITEABLE:                printf("connection established\n");                            // 头文件链接描述            // http://git.warmcat.com/cgi-bin/cgit/libwebsockets/tree/lib/libwebsockets.h#n281            case LWS_CALLBACK_HTTP: {                char *requested_uri = (char *) in;                printf("requested URI: %s\n", requested_uri);       // 喷出访问的URL                                // uri为"/"访问，直接给出hello world                if (strcmp(requested_uri, "/") == 0) {                    void *universal_response = "Hello, World!";                    // http://git.warmcat.com/cgi-bin/cgit/libwebsockets/tree/lib/libwebsockets.h#n597                    libwebsocket_write(wsi, universal_response,                                       strlen(universal_response), LWS_WRITE_HTTP);                    break;                    } else {                    // try to get current working directory                    char cwd[1024];                    char *resource_path;                                        if (getcwd(cwd, sizeof(cwd)) != NULL) {                        // allocate enough memory for the resource path                        // 动态分配路径存储空间                        resource_path = malloc(strlen(cwd) + strlen(requested_uri));                                                // join current working direcotry to the resource path                        // 合成资源路径                        sprintf(resource_path, "%s%s", cwd, requested_uri);                        printf("resource path: %s\n", resource_path);                                                // 获取文件扩展名                        char *extension = strrchr(resource_path, ‘.‘);                        char *mime;                                                // choose mime type based on the file extension                        // 设置扩展类型                        if (extension == NULL) {                            mime = "text/plain";                        } else if (strcmp(extension, ".png") == 0) {                            mime = "image/png";                        } else if (strcmp(extension, ".jpg") == 0) {                            mime = "image/jpg";                        } else if (strcmp(extension, ".gif") == 0) {                            mime = "image/gif";                        } else if (strcmp(extension, ".html") == 0) {                            mime = "text/html";                        } else if (strcmp(extension, ".css") == 0) {                            mime = "text/css";                        } else {                            mime = "text/plain";                        }                                                // by default non existing resources return code 400                        // for more information how this function handles headers                        // see it‘s source code                        // http://git.warmcat.com/cgi-bin/cgit/libwebsockets/tree/lib/parsers.c#n1896                        libwebsockets_serve_http_file(wsi, resource_path, mime);                                            }                }                                // close connection                // 关闭连接                libwebsocket_close_and_free_session(context, wsi,                                                    LWS_CLOSE_STATUS_NORMAL);                break;            }            default:                printf("unhandled callback\n");                break;        }                return 0;    }        /* list of supported protocols and callbacks */    // 配置协议以及其回调函数    static struct libwebsocket_protocols protocols[] = {        /* first protocol must always be HTTP handler */                {            "http-only",    /* name */            callback_http,  /* callback */            0               /* per_session_data_size */        },        {            NULL, NULL, 0   /* End of list */        }            };        int main(void) {        // server url will be http://localhost:7681        int port = 8080;        const char *interface = NULL;        struct libwebsocket_context *context;         // we‘re not using ssl        const char *cert_path = NULL;        const char *key_path = NULL;        // no special options        int opts = 0;                // create libwebsocket context representing this server        // 创建上下文        context = libwebsocket_create_context(port, interface, protocols,                                              libwebsocket_internal_extensions,                                              cert_path, key_path, -1, -1, opts);                if (context == NULL) {            fprintf(stderr, "libwebsocket init failed\n");            return -1;        }                printf("starting server...\n");                // infinite loop, the only option to end this serer is        // by sending SIGTERM. (CTRL+C)        while (1) {            libwebsocket_service(context, 50);            // libwebsocket_service will process all waiting events with their            // callback functions and then wait 50 ms.            // (this is single threaded webserver and this will keep            // our server from generating load while there are not            // requests to process)        }                libwebsocket_context_destroy(context);                return 0;    }