libwebsockets libwebsockets-webserver.c hacking

/**********************************************************************************
*                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;
}