工作流程：
1>服务器启动，在指定端口或随机选取端口绑定httpd服务。
2>收到一个http请求时(其实就是listen端口accept的时候)，派生一个线程运行accept_request函数。
3>取出http请求中method(get或post)和url,对于get方法，如果有携带参数，则query_string指针指向url中?后面的get参数。
4>格式化url到path数组，表示浏览器请求的文件路径，在tinyhttpd中服务器文件是在htdocs文件夹下。当url以/结尾，或者url是个目录，则默认在path中加上index.thml，表示访问主页。
5>如果文件路径合法，对于无参数的get请求，直接输出服务器文件到浏览器，即用http格式写到套接字上，跳到(10)。其他情况(带参数get，post方法，url为科执行文件)，则调用execute_cgi函数执行cgi脚本。
6>读取整个http请求并丢弃，如果是post则找出content-length，把http状态码200写到套接字里面。
7>建立两个管道，cgi_input和cgi_output,并fork一个子进程。
8>在子进程中，把stdout重定向到cgi_output的写入端，把stdin重定向到cgi_input的读取端，关闭cgi_input的写入端和cgi_output的读取端，是指request_method的环境变量，get的话设置query_string的环境变量，post的话设置content-length的环境变量，这些环境变量都是为了给cgi脚本调用，接着用execl运行cgi程序。
9>在父进程中，关闭cgi_input的读取端和cgi_output的写入端，如果post的话，把post数据写入到cgo_input，已被重定向到stdin读取cgi_output的管道输出到客户端，等待子进程结束。
10>关闭与浏览器的链接，完成一次http请求与回应，因为http是无连接的。
1 /* J. David‘s webserver */
2 /* This is a simple webserver.
3 * Created November 1999 by J. David Blackstone.
4 * CSE 4344 (Network concepts), Prof. Zeigler
5 * University of Texas at Arlington
6 */
7 /* This program compiles for Sparc Solaris 2.6.
8 * To compile for Linux:
9 * 1) Comment out the #include <pthread.h> line.
10 * 2) Comment out the line that defines the variable newthread.
11 * 3) Comment out the two lines that run pthread_create().
12 * 4) Uncomment the line that runs accept_request().
13 * 5) Remove -lsocket from the Makefile.
14 */
15 #include <stdio.h>
16 #include <sys/socket.h>
17 #include <sys/types.h>
18 #include <netinet/in.h>
19 #include <arpa/inet.h>
20 #include <unistd.h>
21 #include <ctype.h>
22 #include <strings.h>
23 #include <string.h>
24 #include <sys/stat.h>
25 #include <pthread.h>
26 #include <sys/wait.h>
27 #include <stdlib.h>
28
29 #define ISspace(x) isspace((int)(x))
30
31 #define SERVER_STRING "Server: jdbhttpd/0.1.0\r\n"
32
33 void accept_request(int);
34 //处理从套接字上监听到的一个HTTP请求，在这里可以很大一部分的体现服务器处理请求的流程
35 void bad_request(int);
36 //返回给客户端这是个错误请求，HTTP状态码是400 BAD REQUEST
37 void cat(int, FILE *);
38 //读取服务器上某个文件写到socket套接字
39 void cannot_execute(int);
40 //主要执行在处理cgi程序的处理，也是个主要函数
41 void error_die(const char *);
42 //把错误信息写到perror并退出
43 void execute_cgi(int, const char *, const char *, const char *);
44 //运行cgi程序的处理，也是哥主函数
45 int get_line(int, char *, int);
46 //读取套接字的一行，把回车换行等情况都统一为换行符结束
47 void headers(int, const char *);
48 //把HTTP相应头写到套接字
49 void not_found(int);
50 //主要处理找不到请求的文件时的情况
51 void serve_file(int, const char *);
52 //调用cat把服务器文件返回给浏览器
53 int startup(u_short *);
54 //初始化httpd服务，包括建立套接字，绑定端口，进行监听等
55 void unimplemented(int);
56 //返回给浏览器表示接收到的http请求所用的method不被支持
57
58 /**********************************************************************/
59 /* A request has caused a call to accept() on the server port to
60 * return. Process the request appropriately.
61 * Parameters: the socket connected to the client */
62 /**********************************************************************/
63 void accept_request(int client)
64 {
65
66 char buf[1024];
67 int numchars;
68 char method[255];
69 char url[255];
70 char path[512];
71 size_t i, j;
72 struct stat st;
73 int cgi = 0; /* becomes true if server decides this is a CGI
74 * program */
75 char *query_string = NULL;
76
77 numchars = get_line(client, buf, sizeof(buf));
78 //读取 client端发送的数据并且 返回的参数是 numchars
79 i = 0;
80 j = 0;
81 while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
82 {
83 method[i] = buf[j];
84 i++;
85 j++;
86 }
87 //得到传递的参数是post 还是get方法 还是其他
88 method[i] = ‘\0‘;
89
90 if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
91 {
92 //回给浏览器表明收到的 HTTP 请求所用的 method 不被支持
93 unimplemented(client);
94 return;
95 }
96
97 if (strcasecmp(method, "POST") == 0)
98 cgi = 1;
99
100 i = 0;
101 //http请求行格式是 method urI http-version
102 while (ISspace(buf[j]) && (j < sizeof(buf)))
103 j++;
104 while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
105 {
106 url[i] = buf[j]; //包含请求行中的URI
107 i++;
108 j++;
109 }
110 url[i] = ‘\0‘;
111 ///获取发送数据中的URI
112 if (strcasecmp(method, "GET") == 0)
113 {
114 //get方法 是将参数传递在URI中的？后面如果元素多用&进行链接
115 query_string = url;
116 while ((*query_string != ‘?‘) && (*query_string != ‘\0‘))
117 query_string++;
118 // get 请求？ 后面为参数
119 if (*query_string == ‘?‘)
120 {
121 cgi = 1;
122 *query_string = ‘\0‘;
123 query_string++;
124 }
125 }
126 //格式url存储在path数组 并且html存储在 htdocs文件中
127 sprintf(path, "htdocs%s", url);
128 if (path[strlen(path) - 1] == ‘/‘)
129 strcat(path, "index.html"); //字符串进行衔接 + index.html
130 //stat函数 根据path路径 获取文件内容 存储在 st 结构体中 成功返回0 错误返回-1
131 if (stat(path, &st) == -1)
132 {
133 while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
134 numchars = get_line(client, buf, sizeof(buf));
135 not_found(client);
136 }
137 else
138 {
139 if ((st.st_mode & S_IFMT) == S_IFDIR)
140 strcat(path, "/index.html");
141 //文件的权限 属主 属组 其它 三种任一个拥有执行权
142 if ((st.st_mode & S_IXUSR) ||
143 (st.st_mode & S_IXGRP) ||
144 (st.st_mode & S_IXOTH) )
145 cgi = 1;
146 //调用cat 把服务器文件返回给浏览器 post方法或者拥有执行权限
147 if (!cgi)
148 serve_file(client, path);
149 else
150 execute_cgi(client, path, method, query_string)
151 //运行cgi程序的处理，也是个主要函数
152 }
153
154 close(client);
155 }
156
157 /**********************************************************************/
158 /* Inform the client that a request it has made has a problem.
159 * Parameters: client socket */
160 /**********************************************************************/
161 void bad_request(int client)
162 {
163 char buf[1024];
164
165 sprintf(buf, "HTTP/1.0 400 BAD REQUEST\r\n");
166 send(client, buf, sizeof(buf), 0);
167 sprintf(buf, "Content-type: text/html\r\n");
168 send(client, buf, sizeof(buf), 0);
169 sprintf(buf, "\r\n");
170 send(client, buf, sizeof(buf), 0);
171 sprintf(buf, "<P>Your browser sent a bad request, ");
172 send(client, buf, sizeof(buf), 0);
173 sprintf(buf, "such as a POST without a Content-Length.\r\n");
174 send(client, buf, sizeof(buf), 0);
175 }
176
177 /**********************************************************************/
178 /* Put the entire contents of a file out on a socket. This function
179 * is named after the UNIX "cat" command, because it might have been
180 * easier just to do something like pipe, fork, and exec("cat").
181 * Parameters: the client socket descriptor
182 * FILE pointer for the file to cat */
183 /**********************************************************************/
184 //读取服务器上的某个文件 写到socket套接字上
185 void cat(int client, FILE *resource)
186 {
187 char buf[1024];
188
189 fgets(buf, sizeof(buf), resource);
190 //检测流上的文件结束符 如果文件结束，则返回非0值，否则返回0，文件结束符只能被clearerr()清除。
191 while (!feof(resource))
192 {
193 send(client, buf, strlen(buf), 0);
194 fgets(buf, sizeof(buf), resource);
195 }
196 }
197
198 /**********************************************************************/
199 /* Inform the client that a CGI script could not be executed.
200 * Parameter: the client socket descriptor. */
201 /**********************************************************************/
202 void cannot_execute(int client)
203 {
204 char buf[1024];
205
206 sprintf(buf, "HTTP/1.0 500 Internal Server Error\r\n");
207 send(client, buf, strlen(buf), 0);
208 sprintf(buf, "Content-type: text/html\r\n");
209 send(client, buf, strlen(buf), 0);
210 sprintf(buf, "\r\n");
211 send(client, buf, strlen(buf), 0);
212 sprintf(buf, "<P>Error prohibited CGI execution.\r\n");
213 send(client, buf, strlen(buf), 0);
214 }
215
216 /**********************************************************************/
217 /* Print out an error message with perror() (for system errors; based
218 * on value of errno, which indicates system call errors) and exit the
219 * program indicating an error. */
220 /**********************************************************************/
221 void error_die(const char *sc)
222 {
223 perror(sc);
224 exit(1);
225 }
226
227 /**********************************************************************/
228 /* Execute a CGI script. Will need to set environment variables as
229 * appropriate.
230 * Parameters: client socket descriptor
231 * path to the CGI script */
232 /**********************************************************************/
233
234 //运行cgi程序 也是个主函数
235 void execute_cgi(int client, const char *path,
236 const char *method, const char *query_string)
237 {
238 //在父进程中，关闭cgi_input的读入端和cgi_output的写入端，如果post的话
239 //把post数据写入到cgi_input，已被重定向到stdin，读取cgi_output的管道
240 //输出到客户端，该管道输入是stdout，接着关闭所有管道，等待子进程结束。
241
242 char buf[1024];
243 int cgi_output[2];
244 int cgi_input[2];
245 //cgi_output[1] cgi_input[1] 为输入端
246 //cgi_input[0] cgi_output[0] 为输出端
247 pid_t pid;
248 int status;
249 int i;
250 char c;
251 int numchars = 1;
252 int content_length = -1;
253
254 buf[0] = ‘A‘;
255 buf[1] = ‘\0‘;
256 //读入请求头
257 if (strcasecmp(method, "GET") == 0)
258 while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
259 numchars = get_line(client, buf, sizeof(buf));
260 else /* POST */
261 {
262 numchars = get_line(client, buf, sizeof(buf));
263 while ((numchars > 0) && strcmp("\n", buf))
264 {
265 buf[15] = ‘\0‘;
266 if (strcasecmp(buf, "Content-Length:") == 0)
267 content_length = atoi(&(buf[16]));
268 numchars = get_line(client, buf, sizeof(buf));
269 }
270 if (content_length == -1)
271 {
272 bad_request(client);
273 return;
274 }
275 }
276
277 sprintf(buf, "HTTP/1.0 200 OK\r\n");
278 send(client, buf, strlen(buf), 0);
279
280 if (pipe(cgi_output) < 0)
281 {
282 cannot_execute(client);
283 return;
284 }
285 if (pipe(cgi_input) < 0)
286 {
287 cannot_execute(client);
288 return;
289 }
290
291 if ( (pid = fork()) < 0 )
292 {
293 cannot_execute(client);
294 return;
295 }
296 if (pid == 0) /* child: CGI script */
297 {
298 char meth_env[255];
299 char query_env[255];
300 char length_env[255];
301 //把stdout重定向到cgi_output的写入端
302 dup2(cgi_output[1], 1);
303 //把stdin重定向到cgi_input的读入端
304 dup2(cgi_input[0], 0);
305 //关闭cgi_output的读入端 和 cgi_input的 写入端
306 close(cgi_output[0]);
307 close(cgi_input[1]);
308 //设置request_method的环境变量
309 sprintf(meth_env, "REQUEST_METHOD=%s", method);
310 putenv(meth_env);
311 if (strcasecmp(method, "GET") == 0)
312 {
313 //设置query_string的环境变量
314 sprintf(query_env, "QUERY_STRING=%s", query_string);
315 putenv(query_env);
316 }
317 else /* POST */
318 {
319 //设置content_length的环境变量
320 sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
321 putenv(length_env);
322 }
323 //用execl运行cgi程序
324 execl(path, path, NULL);
325 exit(0);
326 }
327 else /* parent */
328 {
329 close(cgi_output[1]);
330 close(cgi_input[0]);
331 //关闭cgi_output的 写入端 和 cgi_input的读取端
332 if (strcasecmp(method, "POST") == 0)
333 //接受post的数据
334 for (i = 0; i < content_length; i++)
335 {
336 recv(client, &c, 1, 0);
337 write(cgi_input[1], &c, 1);
338 //讲post数据写入cgi_input，并且重定向到stdin中
339 }
340 //读取cgi_output的管道输出到客户端，该管道输入时stdout
341 while (read(cgi_output[0], &c, 1) > 0)
342 send(client, &c, 1, 0);
343 //关闭管道
344 close(cgi_output[0]);
345 close(cgi_input[1]);
346 //等待子进程
347 waitpid(pid, &status, 0);
348 }
349 }
350
351 /**********************************************************************/
352 /* Get a line from a socket, whether the line ends in a newline,
353 * carriage return, or a CRLF combination. Terminates the string read
354 * with a null character. If no newline indicator is found before the
355 * end of the buffer, the string is terminated with a null. If any of
356 * the above three line terminators is read, the last character of the
357 * string will be a linefeed and the string will be terminated with a
358 * null character.
359 * Parameters: the socket descriptor
360 * the buffer to save the data in
361 * the size of the buffer
362 * Returns: the number of bytes stored (excluding null) */
363 /**********************************************************************/
364 int get_line(int sock, char *buf, int size)
365 {
366 int i = 0;
367 char c = ‘\0‘;
368 int n;
369
370 while ((i < size - 1) && (c != ‘\n‘))
371 {
372 //每次接受一个字符
373 n = recv(sock, &c, 1, 0);
374 /* DEBUG printf("%02X\n", c); */
375 if (n > 0)
376 {
377 if (c == ‘\r‘)
378 {
379 n = recv(sock, &c, 1, MSG_PEEK);
380 /* DEBUG printf("%02X\n", c); */
381 if ((n > 0) && (c == ‘\n‘))
382 recv(sock, &c, 1, 0);
383 else
384 c = ‘\n‘;
385 }
386 buf[i] = c;
387 i++;
388 }
389 else
390 c = ‘\n‘;
391 }
392 buf[i] = ‘\0‘;
393
394 return(i);
395 }
396
397 /**********************************************************************/
398 /* Return the informational HTTP headers about a file. */
399 /* Parameters: the socket to print the headers on
400 * the name of the file */
401 /**********************************************************************/
402 //http 响应体
403 void headers(int client, const char *filename)
404 {
405 char buf[1024];
406 (void)filename; /* could use filename to determine file type */
407
408 strcpy(buf, "HTTP/1.0 200 OK\r\n");//响应的状态行
409 send(client, buf, strlen(buf), 0);
410 strcpy(buf, SERVER_STRING);
411 send(client, buf, strlen(buf), 0);
412 sprintf(buf, "Content-Type: text/html\r\n"); //响应头
413 send(client, buf, strlen(buf), 0);
414 strcpy(buf, "\r\n"); //响应正文段
415 send(client, buf, strlen(buf), 0);
416 }
417
418 /**********************************************************************/
419 /* Give a client a 404 not found status message. */
420 /**********************************************************************/
421 void not_found(int client)
422 {
423 //客户端发送的请求无法实现
424 char buf[1024];
425 //响应行
426 sprintf(buf, "HTTP/1.0 404 NOT FOUND\r\n");
427 send(client, buf, strlen(buf), 0);
428 sprintf(buf, SERVER_STRING);
429 send(client, buf, strlen(buf), 0);
430 //响应头
431 sprintf(buf, "Content-Type: text/html\r\n");
432 send(client, buf, strlen(buf), 0);
433 sprintf(buf, "\r\n");
434 //响应头和响应正文段之间有一个空行 表示响应行结束
435 send(client, buf, strlen(buf), 0);
436 //响应正文段 text/html
437 sprintf(buf, "<HTML><TITLE>Not Found</TITLE>\r\n");
438 send(client, buf, strlen(buf), 0);
439 sprintf(buf, "<BODY><P>The server could not fulfill\r\n");
440 send(client, buf, strlen(buf), 0);
441 sprintf(buf, "your request because the resource specified\r\n");
442 send(client, buf, strlen(buf), 0);
443 sprintf(buf, "is unavailable or nonexistent.\r\n");
444 send(client, buf, strlen(buf), 0);
445 sprintf(buf, "</BODY></HTML>\r\n");
446 send(client, buf, strlen(buf), 0);
447 }
448
449 /**********************************************************************/
450 /* Send a regular file to the client. Use headers, and report
451 * errors to client if they occur.
452 * Parameters: a pointer to a file structure produced from the socket
453 * file descriptor
454 * the name of the file to serve */
455 /**********************************************************************/
456 void serve_file(int client, const char *filename)
457 {
458 FILE *resource = NULL;
459 int numchars = 1;
460 char buf[1024];
461
462 buf[0] = ‘A‘;
463 buf[1] = ‘\0‘;
464 while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
465 numchars = get_line(client, buf, sizeof(buf));
466
467 resource = fopen(filename, "r");
468 if (resource == NULL)
469 not_found(client);
470 else
471 {
472 headers(client, filename);
473 cat(client, resource);
474 }
475 fclose(resource);
476 }
477
478 /**********************************************************************/
479 /* This function starts the process of listening for web connections
480 * on a specified port. If the port is 0, then dynamically allo //响应正文段cate a
481 * port and modify the original port variable to reflect the actual
482 * port.
483 * Parameters: pointer to variable containing the port to connect on
484 * Returns: the socket */
485 /**********************************************************************/
486 int startup(u_short *port)
487 {
488 int httpd = 0;
489 struct sockaddr_in name;
490 //建立套接字
491 httpd = socket(PF_INET, SOCK_STREAM, 0);
492 if (httpd == -1)
493 error_die("socket");
494 memset(&name, 0, sizeof(name));
495 name.sin_family = AF_INET;
496 name.sin_port = htons(*port);
497 name.sin_addr.s_addr = htonl(INADDR_ANY);
498 //绑定端口和ip
499 if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0)
500 error_die("bind");
501 if (*port == 0) /* if dynamically allocating a port */
502 {
503 int namelen = sizeof(name);
504 if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1)
505 error_die("getsockname");
506 *port = ntohs(name.sin_port);
507 }
508 //监听
509 if (listen(httpd, 5) < 0)
510 error_die("listen");
511 return(httpd);
512 }
513
514 /**********************************************************************/
515 /* Inform the client that the requested web method has not been
516 * implemented.
517 * Parameter: the client socket */
518 /**********************************************************************/
519 void unimplemented(int client)
520 {
521 //发回响应信息 http的请求方法不被接受
522 char buf[1024];
523 //返回501 错误 未实现 (Not implemented)是指Web 服务器不理解或不支持发送给它的 HTTP 数据流中找到的 HTTP 方法
524 sprintf(buf, "HTTP/1.0 501 Method Not Implemented\r\n");
525 send(client, buf, strlen(buf), 0);
526 sprintf(buf, SERVER_STRING);
527 send(client, buf, strlen(buf), 0);
528 sprintf(buf, "Content-Type: text/html\r\n");//响应头
529 send(client, buf, strlen(buf), 0);
530 sprintf(buf, "\r\n");
531 send(client, buf, strlen(buf), 0); //响应正文段
532 sprintf(buf, "<HTML><HEAD><TITLE>Method Not Implemented\r\n");
533 send(client, buf, strlen(buf), 0);
534 sprintf(buf, "</TITLE></HEAD>\r\n");
535 send(client, buf, strlen(buf), 0);
536 sprintf(buf, "<BODY><P>HTTP request method not supported.\r\n");
537 send(client, buf, strlen(buf), 0);
538 sprintf(buf, "</BODY></HTML>\r\n");
539 send(client, buf, strlen(buf), 0);
540 }
541
542 /**********************************************************************/
543
544 int main(void)
545 {
546 int server_sock = -1;
547 u_short port = 0;
548 int client_sock = -1;
549 struct sockaddr_in client_name;
550 int client_name_len = sizeof(client_name);
551 pthread_t newthread;
552
553 server_sock = startup(&port);
554 printf("httpd running on port %d\n", port);
555
556 while (1)
557 {
558 client_sock = accept(server_sock,
559 (struct sockaddr *)&client_name,
560 &client_name_len);
561 //建立链接
562 if (client_sock == -1)
563 error_die("accept");
564 /* accept_request(client_sock); */
565 //多线程进行控制
566 if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0)
567 perror("pthread_create");
568 }
569
570 close(server_sock);
571
572 return(0);
573 }
时间： 2024-10-28 14:30:26