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运用writen和readn函数，防止在广域网上出现粘包

分类： LINUX

2015-03-25 17:15:57

功能：实现多客户端连接的回射服务器，防止出现粘包。
server.c

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  1. #include <sys/types.h>
  2. #include <sys/socket.h>
  3. #include <stdio.h>
  4. #include <netinet/in.h>
  5. #include <arpa/inet.h>
  6. #include <unistd.h>
  7. #include <string.h>
  8. #include <stdlib.h>
  9. #include <fcntl.h>
  10. #include <sys/shm.h>
  11. #include<errno.h>

  13. #define MYPORT 8887
  14. #define QUEUE 20
  15. #define BUFFER_SIZE 1024
  16. struct packet
  17. {
  18.     int len;
  19.     char buf[BUFFER_SIZE];
  20. };
  21. ssize_t readn(int fd,void*buf,size_t count) ///用readn函数，防止在广域网上发生粘包
  22. {
  23.     size_t nleft = count;
  24.     ssize_t nread;
  25.     char *bufp =(char*)buf;
  26.     while(nleft>0)
  27.     {
  28.         if((nread =read(fd,bufp,nleft))<0)
  29.         {
  30.             if(errno ==EINTR)
  31.                 continue;
  32.             return -1;
  33.         }
  34.         else if(nread ==0)
  35.             return count - nleft;
  36.             
  37.         bufp +=nread;
  38.         nleft -=nread;
  39.         
  40.     }
  41.     return count;
  42. }
  43. ssize_t writen(int fd,const void*buf,size_t count) ///用writen函数，防止在广域网上发生粘包
  44. {
  45.     size_t nleft=count;
  46.     ssize_t nwritten;
  47.     char *bufp=(char*)buf;
  48.     while(nleft>0)
  49.     {
  50.         if((nwritten =write(fd,bufp,nleft))<0)
  51.         {
  52.             if(errno ==EINTR)
  53.                 continue;
  54.             return -1;
  55.         }
  56.         else if(nwritten ==0)
  57.             continue;
  58.             
  59.         bufp +=nwritten;
  60.         nleft -=nwritten;
  61.         
  62.     }
  63.     return count;
  64. }
  65. void do_service(int conn)
  66. {
  67.     
  68.     struct packet recvbuf;    
  69.     int n;
  70.     while(1)
  71.     {
  72.         memset(&recvbuf,0,sizeof(recvbuf));
  73.         int ret = readn(conn, &recvbuf.len, 4);
  74.         if (ret ==-1)
  75.         {
  76.         perror("read");
  77.         exit(1);
  78.         }
  79.         else if(ret <4)
  80.         {
  81.             printf("client close\n");
  82.         
  83.             break;
  84.         }
  85.         n=ntohl(recvbuf.len);
  86.         ret =readn(conn,recvbuf.buf,n);
  87.         if (ret ==-1)
  88.         {
  89.         perror("read");
  90.         exit(1);
  91.         }
  92.         else if(ret <n)
  93.         {
  94.             printf("client close\n");
  95.         
  96.             break;
  97.         }
  98.         
  99.         fputs(recvbuf.buf, stdout);
  100.         writen(conn, &recvbuf, 4+n);
  101.     }
  102. }
  103. int main()
  104. {
  105.         
  106.     
  107.     ///定义sockfd
  108.     int server_sockfd = socket(AF_INET,SOCK_STREAM, 0);

  110.     ///定义sockaddr_in
  111.     struct sockaddr_in server_sockaddr;
  112.     server_sockaddr.sin_family = AF_INET;
  113.     server_sockaddr.sin_port = htons(MYPORT);
  114.     server_sockaddr.sin_addr.s_addr = inet_addr("127.0.0.2");

  116.     ///bind，成功返回0，出错返回-1
  117.     int on =1; ///获得IP地址和端口
  118.     if(setsockopt(server_sockfd,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(on))==-1)   ///实现IP地址的重复利用，防止出现address used
  119.     {
  120.          perror("setsockopt");
  121.          exit(1);
  122.     }
  123.     printf("ip=%s port=%d\n",inet_ntoa(server_sockaddr.sin_addr),ntohs(server_sockaddr.sin_port));
  124.     if(bind(server_sockfd,(struct sockaddr *)&server_sockaddr,sizeof(server_sockaddr))==-1)
  125.     {
  126.         perror("bind");
  127.         exit(1);
  128.     }

  130.     ///listen，成功返回0，出错返回-1
  131.     int listenfd=listen(server_sockfd,QUEUE) ;
  132.     if(listenfd<0)
  133.     {
  134.         perror("listen");
  135.         exit(1);
  136.     }

  138.     ///客户端套接字
  139.    
  140.     struct sockaddr_in client_addr;
  141.     socklen_t length = sizeof(client_addr);

  143.     ///成功返回非负描述字，出错返回-1
  144.    
  145.     int conn ;
  146.     pid_t pid; ///fork 多个进程
  147.     while(1) ///多个客户端连接
  148.     {     if((conn = accept(server_sockfd, (struct sockaddr*)&client_addr, &length))<0)
  149.      {
  150.           perror("accept");
  151.           exit(1);
  152.          }
  153.           pid =fork();
  154.          if(pid==-1)
  155.      {
  156.             perror("fork");
  157.             exit(1);
  158.            }
  159.          if(pid==0)    ///子进程
  160.          {
  161.              close(server_sockfd);
  162.              do_service(conn);
  163.              exit(1);
  164.          }
  165.          else  ///父进程

  167.              close(conn);
  168.     
  169.     }
  170.     
  171.     return 0;
  172. }

client.c：

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  1. #include <sys/types.h>
  2. #include <sys/socket.h>
  3. #include <stdio.h>
  4. #include <netinet/in.h>
  5. #include <arpa/inet.h>
  6. #include <unistd.h>
  7. #include <string.h>
  8. #include <stdlib.h>
  9. #include <fcntl.h>
  10. #include <sys/shm.h>
  11. #include<errno.h>

  13. #define MYPORT 8887
  14. #define QUEUE 20
  15. #define BUFFER_SIZE 1024
  16. struct packet
  17. {
  18.     int len;
  19.     char buf[BUFFER_SIZE];
  20. };
  21. ssize_t readn(int fd,void*buf,size_t count) ///用readn函数，防止在广域网上发生粘包
  22. {
  23.     size_t nleft = count;
  24.     ssize_t nread;
  25.     char *bufp =(char*)buf;
  26.     while(nleft>0)
  27.     {
  28.         if((nread =read(fd,bufp,nleft))<0)
  29.         {
  30.             if(errno ==EINTR)
  31.                 continue;
  32.             return -1;
  33.         }
  34.         else if(nread ==0)
  35.             return count - nleft;
  36.             
  37.         bufp +=nread;
  38.         nleft -=nread;
  39.         
  40.     }
  41.     return count;
  42. }
  43. ssize_t writen(int fd,const void*buf,size_t count) ///用writen函数，防止在广域网上发生粘包
  44. {
  45.     size_t nleft=count;
  46.     ssize_t nwritten;
  47.     char *bufp=(char*)buf;
  48.     while(nleft>0)
  49.     {
  50.         if((nwritten =write(fd,bufp,nleft))<0)
  51.         {
  52.             if(errno ==EINTR)
  53.                 continue;
  54.             return -1;
  55.         }
  56.         else if(nwritten ==0)
  57.             continue;
  58.             
  59.         bufp +=nwritten;
  60.         nleft -=nwritten;
  61.         
  62.     }
  63.     return count;
  64. }

  66. int main()
  67. {
  68.     ///定义sockfd
  69.      int sock= socket(AF_INET,SOCK_STREAM, 0);
  70.      if (sock<0)
  71.         
  72.          {
  73.         perror("sock");
  74.         exit(1);
  75.     }
  76.     struct sockaddr_in servaddr;
  77.     memset(&servaddr,0,sizeof(servaddr));


  80.     ///定义sockaddr_in
  81.     
  82.     servaddr.sin_family = AF_INET;
  83.     servaddr.sin_port = htons(MYPORT);
  84.     servaddr.sin_addr.s_addr = inet_addr("127.0.0.2");

  86.     ///bind，成功返回0，出错返回-1
  87.     
  88.    if (connect(sock,(struct sockaddr*)&servaddr,sizeof(servaddr))<0)
  89.      {
  90.         perror("connect");
  91.         exit(1);
  92.         } ///获得IP地址和端口
  93.          printf("ip=%s port=%d\n",inet_ntoa(servaddr.sin_addr),ntohs(servaddr.sin_port));
  94.     struct packet sendbuf;
  95.     struct packet recvbuf;
  96.     memset(&sendbuf,0,sizeof(sendbuf));
  97.     memset(&recvbuf,0,sizeof(recvbuf));
  98.     int n;
  99.      while (fgets(sendbuf.buf, sizeof(sendbuf.buf), stdin) != NULL) ///键盘输入
  100.     {
  101.             n=strlen(sendbuf.buf);
  102.             sendbuf.len=htonl(n);
  103.          writen(sock,&sendbuf,4+n);
  104.             int ret = readn(sock, &recvbuf.len, 4);
  105.         if (ret ==-1)
  106.         {
  107.         perror("read");
  108.         exit(1);
  109.         }
  110.         else if(ret <4)
  111.         {
  112.             printf("client close\n");
  113.         
  114.             break;
  115.         }
  116.         n=ntohl(recvbuf.len);
  117.         ret =readn(sock,recvbuf.buf,n);
  118.         if (ret ==-1)
  119.         {
  120.         perror("read");
  121.         exit(1);
  122.         }
  123.         else if(ret <n)
  124.         {
  125.             printf("client close\n");
  126.         
  127.             break;
  128.         }
  129.         
  130.         fputs(recvbuf.buf,stdout);
  131.         memset(&sendbuf,0,sizeof(sendbuf));
  132.         memset(&recvbuf,0,sizeof(recvbuf));
  133.     }
  134.     close(sock);
  135.     return 0;
  136. }

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