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linux socket 编程示例

分类： LINUX

2015-04-16 20:51:29

原文地址：linux socket 编程示例 作者：andersonyan

前言
   socket编程现在几乎成了网络编程的代名词，关于这方面的书籍与资料更是不可胜数。比较好的可以推荐一下《Unix 网络编程 卷1：套接字联网API》。

1. TCP
   TCP提供客户与服务器之间的连接(connection),TCP客户先与某个给定服务器之间建立一个连接，再跨该连接与那个服务器交换数据，然后终止这个连接。
   
1.1 TCP server
编程步骤：
socket→初始化struct  sockaddr_in→bind→listen→[accept→send→recv]
tcp_server.c
  1. /*
  2.  * \brief
  3.  * tcp server
  4.  */
  5. #include <stdio.h>
  6. #include <sys/socket.h>
  7. #include <sys/types.h>
  8. #include <netinet/in.h>
  9. #include <arpa/inet.h>
  10. #include <string.h>
  11. #include <stdlib.h>

  13. #define SERVPORT 8080
  14. #define BACKLOG 10 // max numbef of client connection
  15. #define MAXDATASIZE 100

  17. int main(char argc, char *argv[])
  18. {
  19.   int sockfd, client_fd, addr_size, recvbytes;
  20.   char rcv_buf[MAXDATASIZE], snd_buf[MAXDATASIZE];
  21.   char* val;
  22.   struct sockaddr_in server_addr; 
  23.   struct sockaddr_in client_addr;

  25.   char IPdotdec[20];

  27.   /* create a new socket and regiter it to os .
  28.    * SOCK_STREAM means that supply tcp service,
  29.    * and must connect() before data transfort.
  30.    */
  31.   if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
  32.   {
  33.     perror("socket:");
  34.     exit(1);
  35.   }

  37.   /* setting server's socket */
  38.   server_addr.sin_family = AF_INET;         // IPv4 network protocol
  39.   server_addr.sin_port = htons(SERVPORT);
  40.   server_addr.sin_addr.s_addr = INADDR_ANY; // auto IP detect
  41.   memset(&(server_addr.sin_zero),0, 8);

  43.   if (bind(sockfd, (struct sockaddr*)&server_addr, sizeof(struct sockaddr))== -1)
  44.   {
  45.     perror("bind:");
  46.     exit(1);
  47.   }

  49.   /* watting for connection , and server permit to recive the requestion from sockfd */
  50.   if (listen(sockfd, BACKLOG) == -1) // BACKLOG assign thd max number of connection
  51.   {
  52.     perror("listen:");
  53.     exit(1);
  54.   }

  56.   while(1)
  57.   {
  58.     addr_size = sizeof(struct sockaddr_in);

  60.     /* accept the sockfd's connection,
  61.      * return an new socket and assign far host to client_addr
  62.      */
  63.     if ((client_fd = accept(sockfd, (struct sockaddr *)&client_addr, &addr_size)) == -1)
  64.     {
  65.       /* Nonblocking mode */
  66.       perror("accept:");
  67.       continue;
  68.     }

  70.     /* network-digital to ip address */
  71.     inet_ntop(AF_INET, (void*)&client_addr, IPdotdec, 16);
  72.     printf("connetion from:%d : %s\n",client_addr.sin_addr, IPdotdec);

  74.     if (!fork())
  75.     {
  76.       /* child process handle with the client connection */

  78.       /* recive the client's data by client_fd */
  79.       if ((recvbytes = recv(client_fd, rcv_buf, MAXDATASIZE, 0)) == -1)
  80.       {
  81.         perror("recv:");
  82.         exit(1);
  83.       }
  84.       rcv_buf[recvbytes]='\0';
  85.       printf("recv:%s\n", rcv_buf);


  88.       *snd_buf='\0';
  89.       strcat(snd_buf, "welcome");
  90.       /* send the message to far-hosts by client_fd */
  91.       if (send(client_fd, snd_buf, strlen(snd_buf), 0) == -1)
  92.       {
  93.         perror("send:");
  94.         exit(1);
  95.       }
  96.       printf("send:%s\n", snd_buf);

  98.       close(client_fd);
  99.       exit(1);
  100.     }

  102.     close(client_fd);
  103.   }

  105.   return 0;
  106. }
编译：
  1. gcc -g -o tcp_server tcp_server.c
1.2 TCP client
编程步骤：
socket→初始化struct  sockaddr_in→connect→[recv→send]
tcp_client.c
  1. /*
  2.  * \brief
  3.  * tcp client
  4.  */

  6. #include <stdio.h>
  7. #include <stdlib.h>
  8. #include <sys/socket.h>
  9. #include <netdb.h>
  10. #include <string.h>

  12. #define SERVPORT 8080
  13. #define MAXDATASIZE 100

  15. int main(int argc, char *argv[])
  16. {
  17.   int sockfd, recvbytes;
  18.   char rcv_buf[MAXDATASIZE]; /*./client 127.0.0.1 hello */
  19.   char snd_buf[MAXDATASIZE];
  20.   struct hostent *host;             /* struct hostent
  21.                                      * {
  22.                                      * char *h_name; // general hostname
  23.                                      * char **h_aliases; // hostname's alias
  24.                                      * int h_addrtype; // AF_INET
  25.                                      * int h_length;
  26.                                      * char **h_addr_list;
  27.                                      * };
  28.                                      */
  29.   struct sockaddr_in server_addr;

  31.   if (argc < 3)
  32.   {
  33.     printf("Usage:%s [ip address] [any string]\n", argv[0]);
  34.     return 1;
  35.   }

  37.   *snd_buf = '\0';
  38.   strcat(snd_buf, argv[2]);

  40.   if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
  41.   {
  42.     perror("socket:");
  43.     exit(1);
  44.   }

  46.   server_addr.sin_family = AF_INET;
  47.   server_addr.sin_port = htons(SERVPORT);
  48.   inet_pton(AF_INET, argv[1], &server_addr.sin_addr);
  49.   memset(&(server_addr.sin_zero), 0, 8);

  51.   /* create the connection by socket
  52.    * means that connect "sockfd" to "server_addr"
  53.    */
  54.   if (connect(sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
  55.   {
  56.     perror("connect");
  57.     exit(1);
  58.   }

  60.   /**/
  61.   if (send(sockfd, snd_buf, sizeof(snd_buf), 0) == -1)
  62.   {
  63.     perror("send:");
  64.     exit(1);
  65.   }
  66.   printf("send:%s\n", snd_buf);

  68.   if ((recvbytes = recv(sockfd, rcv_buf, MAXDATASIZE, 0)) == -1)
  69.   {
  70.     perror("recv:");
  71.     exit(1);
  72.   }

  74.   rcv_buf[recvbytes] = '\0';
  75.   printf("recv:%s\n", rcv_buf);

  77.   close(sockfd);
  78.   return 0;
  79. }
编译：
  1. gcc -o -g tcp_client tcp_client.c
2. UDP
   UDP提供无连接的(connectionless)服务，比如一个UDP客户可以创建一个套接字并发送一个数据报给一个给定的服务器，然后立即用同一个套接字发送另一个数据报给另一个服务器。同样地，一个UDP服务器可以用同一个UDP套接字从若干不同的客户接收数据报，每个客户一个数据报。

2.1 UDP server
编程步骤：
socket→初始化struct  sockaddr_in→bind→[recvfrom→sendto]
udp_server.c
  1. #include <stdio.h>
  2. #include <sys/socket.h>
  3. #include <netinet/in.h>
  4. #include <string.h>
  5. #include <stdlib.h>


  8. #define SERVPORT 8080
  9. #define MAXDATASIZE 100

  11. int main()
  12. {
  13.   int sockfd, addr_size, recvbytes;
  14.   char rcv_buf[MAXDATASIZE], snd_buf[MAXDATASIZE];
  15.   char* val;
  16.   struct sockaddr_in server_addr;

  18.   if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
  19.   {
  20.     perror("socket:");
  21.     exit(1);
  22.   }

  24.   server_addr.sin_family = AF_INET;
  25.   server_addr.sin_port = htons(SERVPORT);
  26.   server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
  27.   memset(&(server_addr.sin_zero), 0, 8);

  29.   if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr))==-1)
  30.   {
  31.     perror("bind:");
  32.     exit(1);
  33.   }

  35.   while(1)
  36.   {
  37.     addr_size = sizeof(struct sockaddr);

  39.     /* receive the data from "server_addr" by "sockfd" and store into "rcv_buf" */
  40.     if ((recvbytes = recvfrom(sockfd, rcv_buf, MAXDATASIZE, 0,
  41.               (struct sockaddr*)&server_addr, &addr_size)) == -1)
  42.     {
  43.       perror("recv:");
  44.       exit(1);
  45.     }
  46.     rcv_buf[recvbytes] = '\0';
  47.     printf("recv:%s : %s\n", inet_ntop(server_addr.sin_addr), rcv_buf);

  49.     *snd_buf = '\0';
  50.     strcat(snd_buf, "welcome");

  52.     /* send the data "snd_buf" to "server_addr" by "sockfd" */
  53.     if (sendto(sockfd, snd_buf, strlen(snd_buf), 0,
  54.             (struct sockaddr*)&server_addr, addr_size) == -1)
  55.     {
  56.       perror("send:");
  57.       exit(1);
  58.     }
  59.     printf("send:%s\n", snd_buf);
  60.     //exit(1);
  61.   }
  62.   close(sockfd);
  63.   return 0;
  64. }
编译：
  1. gcc -g -o udp_server udp_server.c
2.2 UDP client
编程步骤：
socket→初始化struct  sockaddr_in→[sendto→recvfrom]
udp_client.c
  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <sys/socket.h>
  4. #include <netdb.h>
  5. #include <string.h>

  7. #define SERVPORT 8080
  8. #define MAXDATASIZE 100

  10. int main(int argc, char *argv[])
  11. {
  12.   int server_sockfd, recvbytes,addr_size;
  13.   char rcv_buf[MAXDATASIZE]; /*./client 127.0.0.1 hello*/
  14.   char snd_buf[MAXDATASIZE];
  15.   struct hostent *host;
  16.   struct sockaddr_in server_addr;

  18.   if (argc < 3)
  19.   {
  20.     printf("Usage:%s [ip address] [any string]\n",argv[0]);
  21.     return 1;
  22.   }
  23.   *snd_buf = '\0';
  24.   strcat(snd_buf,argv[2]);

  26.   if ((server_sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
  27.   {
  28.     perror("socket:");
  29.     exit(1);
  30.   }

  32.   server_addr.sin_family=AF_INET;
  33.   server_addr.sin_port=htons(SERVPORT);
  34.   inet_pton(AF_INET,argv[1],&server_addr.sin_addr);
  35.   memset(&(server_addr.sin_zero),0,8);
  36.   addr_size=sizeof(struct sockaddr);

  38.   /* send the data "snd_buf" to "server_addr" by server_sockfd */
  39.   if (sendto(server_sockfd,snd_buf,sizeof(snd_buf),0,
  40.           (struct sockaddr*)&server_addr,addr_size) == -1)
  41.   {
  42.     perror("send:");
  43.     exit(1);
  44.   }
  45.   printf("send:%s\n",snd_buf);

  47.   /* receive the data from "server_addr" by "server_sockfd" and store into rcv_buf */
  48.   if ((recvbytes=recvfrom(server_sockfd,rcv_buf,MAXDATASIZE,0,
  49.             (struct sockaddr*)&server_addr,&addr_size)) ==-1)
  50.   {
  51.     perror("recv:");
  52.     exit(1);
  53.   }
  54.   rcv_buf[recvbytes] = '\0';
  55.   printf("recv:%s\n",rcv_buf);

  57.   close(server_sockfd);
  58.   return 0;
  59. }
编译：
  1. gcc -g -o udp_client udp_client.c
3. UDP multicast
  有时候，本机不止有一张网卡，所以接收UDP组播的数据先要将本机指定的网卡地址加入组播组，才能接收到组播数据。
编程步骤：
socket-->setsockopt-->bind->setsockopt(本机网卡加入组播组)-->[recvfrom --> sendto]
udp_multicast_recv.c
  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4. #include <sys/socket.h>
  5. #include <sys/types.h>
  6. #include <netinet/in.h>
  7. #include <arpa/inet.h>

  9. #define UDPMCASTPORT 1234
  10. #define MAXDATASIZE 1024



  14. int main(char argc, char *argv[])
  15. {
  16.   int udp_sockfd, addr_size, recvbytes;
  17.   char rcv_buf[MAXDATASIZE];

  19.   struct sockaddr_in servaddr, clitaddr;
  20.   struct ip_mreq mreq;

  22.   char* pc_udpmcaddr = "225.1.1.31";
  23.   char* pc_udpmcport = "1234";
  24.   char* pc_localaddr = "192.168.1.73";
  25.   int i_reuse_socket;


  28.   if (argc != 3)
  29.   {
  30.     fprintf(stdout, "SYNTAX: ./udp_mcast_recv \n");
  31.     exit(1);
  32.   }
  33.   else
  34.   {
  35.     pc_udpmcaddr = argv[1];
  36.     pc_localaddr = argv[2];
  37.   }

  39.   memset(&servaddr, 0, sizeof(struct sockaddr_in));
  40.   memset(&clitaddr, 0, sizeof(struct sockaddr_in));
  41.   memset(&mreq, 0, sizeof(struct ip_mreq));

  43.   /* create socket */
  44.   if ((udp_sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
  45.   {
  46.     perror("socket:");
  47.     exit(1);
  48.   }

  50.   i_reuse_socket = 1;
  51.   if (setsockopt(udp_sockfd, SOL_SOCKET, SO_REUSEADDR, &i_reuse_socket, sizeof(int))== -1)
  52.   {
  53.     perror("setsockopt:");
  54.     exit(1);
  55.   }

  57.   servaddr.sin_family = AF_INET;
  58.   servaddr.sin_port = htons(UDPMCASTPORT);

  60.   if (!inet_aton(pc_udpmcaddr, &servaddr.sin_addr))
  61.   {
  62.     perror("inet_aton:");
  63.     exit(1);
  64.   }
  65.   if (bind(udp_sockfd, (struct sockaddr *)&servaddr, sizeof(struct sockaddr))==-1)
  66.   {
  67.     perror("bind:");
  68.     exit(1);
  69.   }

  71.   if (!inet_aton(pc_udpmcaddr, &mreq.imr_multiaddr))
  72.   {
  73.     perror("inet_aton:");
  74.     exit(1);
  75.   }

  77.   if (!inet_aton(pc_localaddr, &mreq.imr_interface))
  78.   {
  79.     perror("inet_aton:");
  80.     exit(1);
  81.   }

  83.   if (setsockopt(udp_sockfd, SOL_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq))==-1)
  84.   {
  85.     perror("setsockopt:");
  86.     exit(1);
  87.   }

  89.   addr_size = sizeof(struct sockaddr);

  91.   while(1)
  92.   {
  93.     if ((recvbytes = recvfrom(udp_sockfd, rcv_buf, MAXDATASIZE, 0,
  94.               (struct sockaddr*)&clitaddr, &addr_size)) == -1)
  95.     {
  96.       perror("recvfrom:");
  97.       exit(1);
  98.     }
  99.     rcv_buf[recvbytes] = '\0';
  100.     fprintf(stdout, "recvfrom:%s:%s", inet_ntoa(clitaddr.sin_addr), rcv_buf);
  101.   }
  102. }
编译：
  1. gcc -g -o udp_multicast_recv udp_multicast_recv.c


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