socket编程

1.TCP

服务端程序：

int main()
{
  /* delete the socket file */
  unlink("server_socket"); 
  /* create a socket */
  int server_sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
  struct sockaddr_un server_addr;
  server_addr.sun_family = AF_UNIX;
  strcpy(server_addr.sun_path, "server_socket"); 
  /* bind with the local file */
  bind(server_sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)); 
  /* listen */
  listen(server_sockfd, 5); 
  char ch;
  int client_sockfd;
  struct sockaddr_un client_addr;
  socklen_t len = sizeof(client_addr);
  while(1)
  {
    printf("server waiting:\n");   
    /* accept a connection */
    client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_addr, &len);   
    /* exchange data */
    read(client_sockfd, &ch, 1);
    printf("get char from client: %c\n", ch);
    ++ch;
    write(client_sockfd, &ch, 1);   
    /* close the socket */
    close(client_sockfd);
  }
  return 0;
}
客户端程序：
int main()
{
  /* create a socket */
  int sockfd = socket(AF_UNIX, SOCK_STREAM, 0); 
  struct sockaddr_un address;
  address.sun_family = AF_UNIX;
  strcpy(address.sun_path, "server_socket"); 
  /* connect to the server */
  int result = connect(sockfd, (struct sockaddr *)&address, sizeof(address));
  if(result == -1)
  {
    perror("connect failed: ");
    exit(1);
  } 
  /* exchange data */
  char ch = 'A';
  write(sockfd, &ch, 1);
  read(sockfd, &ch, 1);
  printf("get char from server: %c\n", ch);
  /* close the socket */
  close(sockfd);
  return 0;
}

2.UDP

服务端：
#define SERV_PORT   8000
int main()
{
  /* socket文件描述符 */
  int sock_fd;
  /* 建立udp socket */
  sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
  if(sock_fd < 0)
  {
    perror("socket");
    exit(1);
  }
  /* 设置address */
  struct sockaddr_in addr_serv;
  int len;
  memset(&addr_serv, 0, sizeof(struct sockaddr_in));
  addr_serv.sin_family = AF_INET;
  addr_serv.sin_port = htons(SERV_PORT);
  /* INADDR_ANY表示不管是哪个网卡接收到数据，只要目的端口是SERV_PORT，就会被该应用程序接收到 */
  addr_serv.sin_addr.s_addr = htonl(INADDR_ANY);
  len = sizeof(addr_serv);
 
  /* 绑定socket */
  if(bind(sock_fd, (struct sockaddr *)&addr_serv, sizeof(addr_serv)) < 0)
  {
    perror("bind error:");
    exit(1);
  }
  int recv_num;
  int send_num;
  char send_buf[20] = "i am server!";
  char recv_buf[20];
  struct sockaddr_in addr_client;
  while(1)
  {
    printf("server wait:\n");  
    recv_num = recvfrom(sock_fd, recv_buf, sizeof(recv_buf), 0, (struct sockaddr *)&addr_client, (socklen_t *)&len);  
    if(recv_num < 0)
    {
      perror("recvfrom error:");
      exit(1);
    }
    recv_buf[recv_num] = '\0';
    printf("server receive %d bytes: %s\n", recv_num, recv_buf);
    send_num = sendto(sock_fd, send_buf, recv_num, 0, (struct sockaddr *)&addr_client, len);  
    if(send_num < 0)
    {
      perror("sendto error:");
      exit(1);
    }
  } 
  close(sock_fd);
  return 0;
}
客户端：
#define DEST_PORT 8000
#define DSET_IP_ADDRESS  "127.0.0.1"
int main()
{
  /* socket文件描述符 */
  int sock_fd;
  /* 建立udp socket */
  sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
  if(sock_fd < 0)
  {
    perror("socket");
    exit(1);
  }
  /* 设置address */
  struct sockaddr_in addr_serv;
  int len;
  memset(&addr_serv, 0, sizeof(addr_serv));
  addr_serv.sin_family = AF_INET;
  addr_serv.sin_addr.s_addr = inet_addr(DSET_IP_ADDRESS);
  addr_serv.sin_port = htons(DEST_PORT);
  len = sizeof(addr_serv);
  int send_num;
  int recv_num;
  char send_buf[20] = "hey, who are you?";
  char recv_buf[20];  
  printf("client send: %s\n", send_buf);
  send_num = sendto(sock_fd, send_buf, strlen(send_buf), 0, (struct sockaddr *)&addr_serv, len); 
  if(send_num < 0)
  {
    perror("sendto error:");
    exit(1);
  } 
  recv_num = recvfrom(sock_fd, recv_buf, sizeof(recv_buf), 0, (struct sockaddr *)&addr_serv, (socklen_t *)&len); 
  if(recv_num < 0)
  {
    perror("recvfrom error:");
    exit(1);
  } 
  recv_buf[recv_num] = '\0';
  printf("client receive %d bytes: %s\n", recv_num, recv_buf); 
  close(sock_fd);
  return 0;
}