下载地址：http://sourceforge.net/projects/tinyhttpd/
/* J. David's webserver */ /* This is a simple webserver. * Created November 1999 by J. David Blackstone. * CSE 4344 (Network concepts), Prof. Zeigler * University of Texas at Arlington */ /* This program compiles for Sparc Solaris 2.6. * To compile for Linux: * 1) Comment out the #include <pthread.h> line. * 2) Comment out the line that defines the variable newthread. * 3) Comment out the two lines that run pthread_create(). * 4) Uncomment the line that runs accept_request(). * 5) Remove -lsocket from the Makefile. */ #include <stdio.h> #include <sys/socket.h> #include <sys/types.h> #include <netinet/in.h> #include <arpa/inet.h> #include <unistd.h> #include <ctype.h> #include <strings.h> #include <string.h> #include <sys/stat.h> // #include <pthread.h> #include <sys/wait.h> #include <stdlib.h> #define ISspace(x) isspace((int)(x)) #define SERVER_STRING "Server: jdbhttpd/0.1.0 " void accept_request(int); void bad_request(int); void cat(int, FILE *); void cannot_execute(int); void error_die(const char *); void execute_cgi(int, const char *, const char *, const char *); int get_line(int, char *, int); void headers(int, const char *); void not_found(int); void serve_file(int, const char *); int startup(u_short *); 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; numchars = get_line(client, buf, sizeof(buf)); i = 0; j = 0; while (!ISspace(buf[j]) && (i < sizeof(method) - 1)) { method[i] = buf[j]; i++; j++; } method[i] = ' '; if (strcasecmp(method, "GET") && strcasecmp(method, "POST")) { unimplemented(client); return; } if (strcasecmp(method, "POST") == 0) { cgi = 1; } i = 0; while (ISspace(buf[j]) && (j < sizeof(buf))) { j++; } while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf))) { url[i] = buf[j]; i++; j++; } url[i] = ' '; if (strcasecmp(method, "GET") == 0) { query_string = url; while ((*query_string != '?') && (*query_string != ' ')) { query_string++; } if (*query_string == '?') { cgi = 1; *query_string = ' '; query_string++; } } sprintf(path, "htdocs%s", url); if (path[strlen(path) - 1] == '/') { strcat(path, "index.html"); } if (stat(path, &st) == -1) { while ((numchars > 0) && strcmp(" ", buf)) /* read & discard headers */ { numchars = get_line(client, buf, sizeof(buf)); } not_found(client); } else { 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) serve_file(client, path); else 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 "); send(client, buf, sizeof(buf), 0); sprintf(buf, "Content-type: text/html "); send(client, buf, sizeof(buf), 0); sprintf(buf, " "); send(client, buf, sizeof(buf), 0); sprintf(buf, "<P>Your browser sent a bad request, "); send(client, buf, sizeof(buf), 0); sprintf(buf, "such as a POST without a Content-Length. "); 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]; fgets(buf, sizeof(buf), resource); 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 "); send(client, buf, strlen(buf), 0); sprintf(buf, "Content-type: text/html "); send(client, buf, strlen(buf), 0); sprintf(buf, " "); send(client, buf, strlen(buf), 0); sprintf(buf, "<P>Error prohibited CGI execution. "); 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) { perror(sc); exit(1); } /**********************************************************************/ /* 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] = ' '; if (strcasecmp(method, "GET") == 0) { while ((numchars > 0) && strcmp(" ", buf)) /* read & discard headers */ { numchars = get_line(client, buf, sizeof(buf)); } } else /* POST */ { numchars = get_line(client, buf, sizeof(buf)); while ((numchars > 0) && strcmp(" ", buf)) { buf[15] = ' '; 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 "); 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 = ' '; int n; while ((i < size - 1) && (c != ' ')) { n = recv(sock, &c, 1, 0); /* DEBUG printf("%02X ", c); */ if (n > 0) { if (c == ' ') { n = recv(sock, &c, 1, MSG_PEEK); /* DEBUG printf("%02X ", c); */ if ((n > 0) && (c == ' ')) recv(sock, &c, 1, 0); else c = ' '; } buf[i] = c; i++; } else c = ' '; } buf[i] = ' '; 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 "); send(client, buf, strlen(buf), 0); strcpy(buf, SERVER_STRING); send(client, buf, strlen(buf), 0); sprintf(buf, "Content-Type: text/html "); send(client, buf, strlen(buf), 0); strcpy(buf, " "); 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 "); send(client, buf, strlen(buf), 0); sprintf(buf, SERVER_STRING); send(client, buf, strlen(buf), 0); sprintf(buf, "Content-Type: text/html "); send(client, buf, strlen(buf), 0); sprintf(buf, " "); send(client, buf, strlen(buf), 0); sprintf(buf, "<HTML><TITLE>Not Found</TITLE> "); send(client, buf, strlen(buf), 0); sprintf(buf, "<BODY><P>The server could not fulfill "); send(client, buf, strlen(buf), 0); sprintf(buf, "your request because the resource specified "); send(client, buf, strlen(buf), 0); sprintf(buf, "is unavailable or nonexistent. "); send(client, buf, strlen(buf), 0); sprintf(buf, "</BODY></HTML> "); 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] = ' '; while ((numchars > 0) && strcmp(" ", buf)) /* read & discard headers */ { numchars = get_line(client, buf, sizeof(buf)); } resource = fopen(filename, "r"); if (resource == NULL) { not_found(client); } else { // 给客户端发送头部 headers(client, filename); // 给客户端发送内容 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; struct sockaddr_in name; httpd = socket(PF_INET, SOCK_STREAM, 0); if (httpd == -1) error_die("socket"); memset(&name, 0, sizeof(name)); name.sin_family = AF_INET; name.sin_port = htons(*port); name.sin_addr.s_addr = htonl(INADDR_ANY); if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0) { error_die("bind"); } if (*port == 0) /* if dynamically allocating a port */ { int namelen = sizeof(name); if (getsockname(httpd, (struct sockaddr *)&name, (socklen_t*)&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) // 针对没有实现的方式做的回复（即除了GET和POST） { char buf[1024]; sprintf(buf, "HTTP/1.0 501 Method Not Implemented "); send(client, buf, strlen(buf), 0); sprintf(buf, SERVER_STRING); send(client, buf, strlen(buf), 0); sprintf(buf, "Content-Type: text/html "); send(client, buf, strlen(buf), 0); sprintf(buf, " "); send(client, buf, strlen(buf), 0); sprintf(buf, "<HTML><HEAD><TITLE>Method Not Implemented "); send(client, buf, strlen(buf), 0); sprintf(buf, "</TITLE></HEAD> "); send(client, buf, strlen(buf), 0); sprintf(buf, "<BODY><P>HTTP request method not supported. "); send(client, buf, strlen(buf), 0); sprintf(buf, "</BODY></HTML> "); send(client, buf, strlen(buf), 0); } /**********************************************************************/ int main(void) { 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 ", port); while (1) { client_sock = accept(server_sock, (struct sockaddr *)&client_name, (socklen_t*)&client_name_len); if (client_sock == -1) { error_die("accept"); } accept_request(client_sock); /* if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0) perror("pthread_create"); */ } close(server_sock); return(0); }
这是一个非常简单的服务器，只是实现了服务器的工作原理。没有考虑其他的性能等问题，全部500行代码左右。
执行流程：
1、开启监听端口。
2、接收客户端连接。
3、解析客户端连接地址，判断是GET还是POST，或者其他，则返回错误，仅支持GET和POST。
4、判断是返回一个网页，还是调用CGI脚本，根据传过来的参数执行。
5、结束。
其中示例CGI脚本是用perl写的。功能就是根据客户端传过来的颜色值设置将要返回的网页的背景色。
其实服务器的执行流程或者说工作原理很简单，它其实就是使用socket来通信，但是通信的内容需要符合HTTP协议，即客户端--服务器交互使用的信息需要有HTTP协议头，其中协议头包含了请求的方法（GET、POST），请求的网页或者文件的路径等。