源码阅读-tinyhttpd

tinyhttpd 是一个不到 500 行的超轻量型 Http Server很适合初学者,帮助我们快速掌握unix socket编程 和 http请求流程。看完所有源码,真的感觉有很大收获,无论是 unix 的编程,还是 GET/POST 的 Web 处理流程,都清晰了不少。

直接从github下载

注释源码如下:

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define ISspace(x) isspace((int)(x))
#define SERVER_STRING "Server: jdbhttpd/0.1.0\r\n"
// 从套接字监听HTTP请求
void accept_request(int);
// 返回错误请求代码
void bad_request(int);
// 读取服务器上的文件到套接字
void cat(int, FILE *);
// 执行cgi发生错误
void cannot_execute(int);
// 吧错误信息写到perror并退出
void error_die(const char *);
// 执行cgi
void execute_cgi(int, const char *, const char *, const char *);
// 读取一行套接字
int get_line(int, char *, int);
// 把http响应头写到套接字
void headers(int, const char *);
// 找不到文件
void not_found(int);
// 调用cat把吴福气文件返回客户端
void serve_file(int, const char *);
// 初始化http server
int startup(u_short *);
// 返回给浏览器表明收到的 HTTP 请求所用的 method 不被支持
void unimplemented(int);
/**********************************************************************/
/* A request has caused a call to accept() on the server port to
 * return.  Process the request appropriately.
 * Parameters: the socket connected to the client */
/**********************************************************************/
void accept_request(int client)
{
    char buf[1024];
    int numchars;
    char method[255];
    char url[255];
    char path[512];
    size_t i, j;
    struct stat st;
    int cgi = 0;      /* becomes true if server decides this is a CGI
                       * program */
    char *query_string = NULL;
    /* 读取一行数据 */
    numchars = get_line(client, buf, sizeof(buf));
    printf("buf:%s\n", buf);
    i = 0; j = 0;
    /* 将数据 复制到method中,直到空格或长度超过 */
    while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
    {
        method[i] = buf[j];
        i++; j++;
    }
    method[i] = '\0';
    printf("method:%s\n", method);
    /* 如果不是GET请求 或 POST请求 */
    if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
    {
        /* 返回请求类型不支持到客户端 */
        printf("uniplemented");
        unimplemented(client);
        return;
    }
    /*如果是POST请求 则执行cgi */
    if (strcasecmp(method, "POST") == 0)
        cgi = 1;

    i = 0;
    /* 转到下一个空格后的数据*/
    /* 跳过空格  */ 
    while (ISspace(buf[j]) && (j < sizeof(buf)))
        j++;
    /* 获取url */
    while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
    {
        url[i] = buf[j];
        i++; j++;
    }
    url[i] = '\0';
    if (strcasecmp(method, "GET") == 0)
    {
        query_string = url;
        /* 获取url参数 */
        while ((*query_string != '?') && (*query_string != '\0'))
            query_string++;
        /* 如果有参数 ,执行cgi*/
        if (*query_string == '?')
        {
            cgi = 1;
            /* 跳过?*/
            *query_string = '\0';
            query_string++;
        }
    }
    /* 生成文件地址path */
    sprintf(path, "htdocs%s", url);
    printf("%s", path);
    /* 如果url为 / 这访问 index.html*/
    if (path[strlen(path) - 1] == '/')
        strcat(path, "index.html");
    /* 打开path文件*/
    if (stat(path, &st) == -1) {
        /* 打开文件失败 */
        while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */
            numchars = get_line(client, buf, sizeof(buf));
        /* 返回403 错误 */
        not_found(client);
    }
    else /* 打开文件成功 */
    {
        if ((st.st_mode & S_IFMT) == S_IFDIR)
            strcat(path, "/index.html");
        if ((st.st_mode & S_IXUSR) ||
            (st.st_mode & S_IXGRP) ||
            (st.st_mode & S_IXOTH)    )
            cgi = 1;
        if (!cgi) /* 发送文件内容到客户端 */
            serve_file(client, path);
        else /* 执行cgi */
            execute_cgi(client, path, method, query_string);
        }

    close(client);
}

/**********************************************************************/
/* Inform the client that a request it has made has a problem.
 * Parameters: client socket */
/**********************************************************************/
void bad_request(int client)
{
    char buf[1024];

    sprintf(buf, "HTTP/1.0 400 BAD REQUEST\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "Content-type: text/html\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "

Your browser sent a bad request, "); send(client, buf, sizeof(buf), 0); sprintf(buf, "such as a POST without a Content-Length.\r\n"); send(client, buf, sizeof(buf), 0); } /**********************************************************************/ /* Put the entire contents of a file out on a socket. This function * is named after the UNIX "cat" command, because it might have been * easier just to do something like pipe, fork, and exec("cat"). * Parameters: the client socket descriptor * FILE pointer for the file to cat */ /**********************************************************************/ void cat(int client, FILE *resource) { char buf[1024]; /* 读取文件内容到buf */ fgets(buf, sizeof(buf), resource); /* 读取玩所有内容并发送到客户端 */ while (!feof(resource)) { send(client, buf, strlen(buf), 0); fgets(buf, sizeof(buf), resource); } } /**********************************************************************/ /* Inform the client that a CGI script could not be executed. * Parameter: the client socket descriptor. */ /**********************************************************************/ void cannot_execute(int client) { char buf[1024]; sprintf(buf, "HTTP/1.0 500 Internal Server Error\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "Content-type: text/html\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "

Error prohibited CGI execution.\r\n"); send(client, buf, strlen(buf), 0); } /**********************************************************************/ /* Print out an error message with perror() (for system errors; based * on value of errno, which indicates system call errors) and exit the * program indicating an error. */ /**********************************************************************/ void error_die(const char *sc) { /* 打印错误信息 */ perror(sc); exit(1); } /**********************************************************************/ /*CGI(Common Gateway Interface 通用网关接口) * 作用: * 提取用户提交的表单信息 * 处理表单信息 * 输出,返回html响应*/ /* Execute a CGI script. Will need to set environment variables as * appropriate. * Parameters: client socket descriptor * path to the CGI script */ /**********************************************************************/ void execute_cgi(int client, const char *path, const char *method, const char *query_string) { char buf[1024]; int cgi_output[2]; int cgi_input[2]; pid_t pid; int status; int i; char c; int numchars = 1; int content_length = -1; buf[0] = 'A'; buf[1] = '\0'; if (strcasecmp(method, "GET") == 0) while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */ numchars = get_line(client, buf, sizeof(buf)); else /* POST */ { numchars = get_line(client, buf, sizeof(buf)); while ((numchars > 0) && strcmp("\n", buf)) { buf[15] = '\0'; if (strcasecmp(buf, "Content-Length:") == 0) content_length = atoi(&(buf[16])); numchars = get_line(client, buf, sizeof(buf)); } if (content_length == -1) { bad_request(client); return; } } sprintf(buf, "HTTP/1.0 200 OK\r\n"); send(client, buf, strlen(buf), 0); if (pipe(cgi_output) < 0) { cannot_execute(client); return; } if (pipe(cgi_input) < 0) { cannot_execute(client); return; } if ( (pid = fork()) < 0 ) { cannot_execute(client); return; } if (pid == 0) /* child: CGI script */ { char meth_env[255]; char query_env[255]; char length_env[255]; dup2(cgi_output[1], 1); dup2(cgi_input[0], 0); close(cgi_output[0]); close(cgi_input[1]); sprintf(meth_env, "REQUEST_METHOD=%s", method); putenv(meth_env); if (strcasecmp(method, "GET") == 0) { sprintf(query_env, "QUERY_STRING=%s", query_string); putenv(query_env); } else { /* POST */ sprintf(length_env, "CONTENT_LENGTH=%d", content_length); putenv(length_env); } execl(path, path, NULL); exit(0); } else { /* parent */ close(cgi_output[1]); close(cgi_input[0]); if (strcasecmp(method, "POST") == 0) for (i = 0; i < content_length; i++) { recv(client, &c, 1, 0); write(cgi_input[1], &c, 1); } while (read(cgi_output[0], &c, 1) > 0) send(client, &c, 1, 0); close(cgi_output[0]); close(cgi_input[1]); waitpid(pid, &status, 0); } } /**********************************************************************/ /* Get a line from a socket, whether the line ends in a newline, * carriage return, or a CRLF combination. Terminates the string read * with a null character. If no newline indicator is found before the * end of the buffer, the string is terminated with a null. If any of * the above three line terminators is read, the last character of the * string will be a linefeed and the string will be terminated with a * null character. * Parameters: the socket descriptor * the buffer to save the data in * the size of the buffer * Returns: the number of bytes stored (excluding null) */ /**********************************************************************/ int get_line(int sock, char *buf, int size) { int i = 0; char c = '\0'; int n; /* 循环读取直到长度超过size或者读到了行末 */ while ((i < size - 1) && (c != '\n')) { /* 获取客户端发送的数据 (获取 1 个字符存放在c中), * flag = 0 从tcp buffer 中复制数据并将它从tcp buffer, * 中移除*/ n = recv(sock, &c, 1, 0); /* DEBUG printf("%02X\n", c); */ if (n > 0)/* 读取到了数据 */ { if (c == '\r')/*如果是行末 读取下一行 */ { /* msg_peek 仅把tcp buffer中的数据督导buf中, * 并不会把读取的数据从tcpbuffer中移除,再次 * 调用时任然读取到的时这个数据 */ n = recv(sock, &c, 1, MSG_PEEK); /* DEBUG printf("%02X\n", c); */ if ((n > 0) && (c == '\n')) /* 如果接收到的是 \r\n则将\n从tcp buffer中移除 */ recv(sock, &c, 1, 0); else c = '\n'; } buf[i] = c; i++; } else c = '\n'; } buf[i] = '\0'; /* 返回读取到的个数 */ return(i); } /**********************************************************************/ /* Return the informational HTTP headers about a file. */ /* Parameters: the socket to print the headers on * the name of the file */ /**********************************************************************/ void headers(int client, const char *filename) { char buf[1024]; (void)filename; /* could use filename to determine file type */ strcpy(buf, "HTTP/1.0 200 OK\r\n"); send(client, buf, strlen(buf), 0); strcpy(buf, SERVER_STRING); send(client, buf, strlen(buf), 0); sprintf(buf, "Content-Type: text/html\r\n"); send(client, buf, strlen(buf), 0); strcpy(buf, "\r\n"); send(client, buf, strlen(buf), 0); } /**********************************************************************/ /* Give a client a 404 not found status message. */ /**********************************************************************/ void not_found(int client) { char buf[1024]; sprintf(buf, "HTTP/1.0 404 NOT FOUND\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, SERVER_STRING); send(client, buf, strlen(buf), 0); sprintf(buf, "Content-Type: text/html\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "Not Found\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "

The server could not fulfill\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "your request because the resource specified\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "is unavailable or nonexistent.\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "\r\n"); send(client, buf, strlen(buf), 0); } /**********************************************************************/ /* Send a regular file to the client. Use headers, and report * errors to client if they occur. * Parameters: a pointer to a file structure produced from the socket * file descriptor * the name of the file to serve */ /**********************************************************************/ void serve_file(int client, const char *filename) { FILE *resource = NULL; int numchars = 1; char buf[1024]; buf[0] = 'A'; buf[1] = '\0'; while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */ numchars = get_line(client, buf, sizeof(buf)); resource = fopen(filename, "r"); if (resource == NULL) not_found(client); else { /* 向客户端发送 header和内容*/ headers(client, filename); cat(client, resource); } fclose(resource); } /**********************************************************************/ /* This function starts the process of listening for web connections * on a specified port. If the port is 0, then dynamically allocate a * port and modify the original port variable to reflect the actual * port. * Parameters: pointer to variable containing the port to connect on * Returns: the socket */ /**********************************************************************/ int startup(u_short *port) { int httpd = 0; /* 文件描述符*/ struct sockaddr_in name; httpd = socket(PF_INET, SOCK_STREAM, 0); /* 出错处理 */ if (httpd == -1) error_die("socket"); /* 清0 */ memset(&name, 0, sizeof(name)); name.sin_family = AF_INET; name.sin_port = htons(*port); name.sin_addr.s_addr = htonl(INADDR_ANY); /* 全网 */ if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0) error_die("bind"); if (*port == 0) /* 如果端口为0 则申请一个临时端口 */ { int namelen = sizeof(name); if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1) error_die("getsockname"); *port = ntohs(name.sin_port); } if (listen(httpd, 5) < 0) error_die("listen"); return(httpd); } /**********************************************************************/ /* Inform the client that the requested web method has not been * implemented. * Parameter: the client socket */ /**********************************************************************/ void unimplemented(int client) { char buf[1024]; sprintf(buf, "HTTP/1.0 501 Method Not Implemented\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, SERVER_STRING); send(client, buf, strlen(buf), 0); sprintf(buf, "Content-Type: text/html\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "Method Not Implemented\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "

HTTP request method not supported.\r\n"); send(client, buf, strlen(buf), 0); sprintf(buf, "\r\n"); send(client, buf, strlen(buf), 0); } /**********************************************************************/ int main(int argc, char argv[]) { int server_sock = -1; u_short port = 0; int client_sock = -1; struct sockaddr_in client_name; int client_name_len = sizeof(client_name); pthread_t newthread; server_sock = startup(&port); printf("httpd running on port %d\n", port); while (1) { /* 开始阻塞接受 */ client_sock = accept(server_sock, (struct sockaddr *)&client_name, &client_name_len); if (client_sock == -1) error_die("accept"); /* 收到客户端连接,创建一个线程处理连接 */ if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0) perror("pthread_create"); } close(server_sock); return(0); }

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