19.1 HTTP

19.1.1 无状态的Stateless协议

所谓的无状态也就是说，服务器响应客户端的请求之后，会断开连接。然后同样的客户端进行第二次请求，就会认为是一个新的连接。

同样，为了弥补HTTP无法保持连接的缺点，Web编程中通常会使用Cookie和Session技术。

19.2 实现简单的Web服务器

19.2.1 实现基于Linux的多线程Web服务器

  1. //webserv_linux.c
  2. #include<stdio.h>
  3. #include<stdlib.h>
  4. #include<unistd.h>
  5. #include<string.h>
  6. #include<arpa/inet.h>
  7. #include<sys/socket.h>
  8. #include<pthread.h>
  10. #define BUF_SIZE 1024
  11. #define SMALL_BUF 100
  13. void *request_handler(void *arg);
  14. void send_data(FILE *fp, char *ct, char *file_name);
  15. char *content_type(char *file);
  16. void send_error(FILE *fp);
  17. void error_handling(char *message);
  19. int main(int argc, char *argv[])
  20. {
  21.     int serv_sock, clnt_sock;
  22.     struct sockaddr_in serv_adr, clnt_adr;
  23.     int clnt_adr_size;
  24.     char buf[BUF_SIZE];
  25.     pthread_t t_id;
  26.     if(argc!=2){
  27.         printf("Usage: %s<port>\n", argv[0]);
  28.         exit(1);
  29.     }
  31.     serv_sock=socket(PF_INET, SOCK_STREAM, 0);
  32.     memset(&serv_adr, 0, sizeof(serv_adr));
  33.     serv_adr.sin_family=AF_INET;
  34.     serv_adr.sin_addr.s_addr=htonl(INADDR_ANY);
  35.     serv_adr.sin_port=htons(atoi(argv[1]));
  36.     if(bind(serv_sock, (struct sockaddr*)&serv_adr, sizeof(serv_adr))==-1)
  37.         error_handling("bind() error");
  38.     if(listen(serv_sock, 20)==-1)
  39.         error_handling("listen() error");
  41.     while(1)
  42.     {
  43.         clnt_adr_size=sizeof(clnt_adr);
  44.         clnt_sock=accept(serv_sock, (struct sockaddr*)&clnt_adr, &clnt_adr_size);
  45.         printf("Connectiion Request: %s:%d\n", inet_ntoa(clnt_adr.sin_addr),ntohs(clnt_adr.sin_port));
  46.         pthread_create(&t_id, NULL, request_handler, &clnt_sock);
  47.     }
  48.     close(serv_sock);
  49.     return 0;
  50. }
  52. void *request_handler(void *arg)
  53. {
  54.     int clnt_sock=*((int*)arg);
  55.     char req_line[SMALL_BUF];
  56.     FILE *clnt_read;
  57.     FILE *clnt_write;
  59.     char method[10];
  60.     char ct[15];
  61.     char file_name[30];
  63.     clnt_read=fdopen(clnt_sock, "r");
  64.     clnt_write=fdopen(dup(clnt_sock), "w");
  65.     fgets(req_line, SMALL_BUF, clnt_read);
  66.     if(strstr(req_line, "HTTP/")==NULL)
  67.     {
  68.         send_error(clnt_write);
  69.         fclose(clnt_read);
  70.         fclose(clnt_write);
  71.         return 0;
  72.     }
  73.     strcpy(method, strtok(req_line, "/"));
  74.     strcpy(file_name, strtok(NULL, "/"));
  75.     strcpy(ct, content_type(file_name));
  76.     if(strcmp(method, "GET")!=0)
  77.     {
  78.         send_error(clnt_write);
  79.         fclose(clnt_read);
  80.         fclose(clnt_write);
  81.         return 0;
  82.     }
  83.     fclose(clnt_read);
  84.     send_data(clnt_write, ct, file_name);
  85. }
  87. void send_data(FILE *fp, char *ct, char *file_name)
  88. {
  89.     char protocol[]="HTTP/1.0 200 OK\r\n";
  90.     char server[]="Server:Linux Web Server \r\n";
  91.     char cnt_len[]="Content-length:2048\r\n";
  92.     char cnt_type[SMALL_BUF];
  93.     char buf[BUF_SIZE];
  94.     FILE *send_file;
  96.     sprintf(cnt_type, "Content-type:%s\r\n\r\n", ct);
  97.     send_file=fopen(file_name, "r");
  98.     if(send_file==NULL)
  99.     {
  100.         send_error(fp);
  101.         return;
  102.     }
  103.     /*请传输头信息*/
  104.     fputs(protocol, fp);
  105.     fputs(server, fp);
  106.     fputs(cnt_len, fp);
  107.     fputs(cnt_type, fp);
  109.     while(fgets(buf, BUF_SIZE, send_file)!=NULL)
  110.     {
  111.         fputs(buf, fp);
  112.         fflush(fp);
  113.     }
  114.     fflush(fp);
  115.     fclose(fp);
  116. }
  118. char *content_type(char *file)
  119. {
  120.     char extension[SMALL_BUF];
  121.     char file_name[SMALL_BUF];
  122.     strcpy(file_name, file);
  123.     strtok(file_name, ".");
  124.     strcpy(extension, strtok(NULL, "."));
  126.     if(!strcmp(extension, "html")||!strcmp(extension,"htm"))
  127.         return "text/html";
  128.     else
  129.         return "text/plain";
  130. }
  132. void send_error(FILE *fp)
  133. {
  134.     char protocol[]="HTTP/1.0 400 Bad Request\r\n";
  135.     char server[]="Server:Linux Web Server\r\n";
  136.     char cnt_len[]="Content-length:2048\r\n";
  137.     char cnt_type[]="Conntent-type:text/html\r\n\r\n";
  138.     char content[]="<html><head><title>NETWORK</title></head>"
  139.     "<body><font size=+5><br>发生错误！查看请求文件名和请求方式！"
  140.     "</font></body></html>";
  142.     fputs(protocol, fp);
  143.     fputs(server, fp);
  144.     fputs(cnt_len, fp);
  145.     fputs(cnt_type, fp);
  146.     fflush(fp);
  147. }
  149. void error_handling(char *message)
  150. {
  151.     fputs(message, stderr);
  152.     fputc('\n', stderr);
  153.     exit(1);
  154. }