linux下用多线程实现socket服务器和客户端的异步通信

来源：互联网发布：unity3d 过山车编辑：程序博客网时间：2024/06/07 04:56

前面介绍了用select函数来实现socket的异步收发数据，但是select函数也有一些缺陷，要使socket能持续地通信，select必须不停地检测，这样进程就会一直阻塞在这里，限制了功能的扩展，这里我们用多线程的方式，另创建两个线程用来发送/接收数据，即可解决这个问题，代码如下：
服务器 server.c

    #include <stdio.h>      #include <stdlib.h>      #include <string.h>      #include <unistd.h>      #include <errno.h>      #include <sys/types.h>      #include <sys/socket.h>      #include <netinet/in.h>      #include <arpa/inet.h>      #include <pthread.h>      void* recvsocket(void *ptr)      {          int fd = *(int *)ptr;          char str[1024];          while (1)          {              memset(str, 0, sizeof(str));              int numbytes = recv(fd, s, sizeof(str), 0);              if (numbytes <= 0)                  break;              printf("%s\n", str);          }          return NULL;      }      void* sendsocket(void *ptr)      {          int fd = *(int *)ptr;          char str[1024];          while (1)          {              memset(s, 0, sizeof(str));              read(STDIN_FILENO, str, sizeof(str));              send(fd, str, strlen(str), 0);          }          return NULL;      }      int main(int arg, char *args[])      {          int port = 1234;          int st = socket(AF_INET, SOCK_STREAM, 0);     int opt = SO_REUSEADDR;    setsockopt(st, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));        struct sockaddr_in addr;         memset(&addr, 0, sizeof(addr));          addr.sin_family = AF_INET;         addr.sin_port = htons(port);          addr.sin_addr.s_addr = htonl(INADDR_ANY);         if (bind(st, (struct sockaddr *) &addr, sizeof(addr)) == -1)          {              printf("bind failed %s\n", strerror(errno));              return EXIT_FAILURE;          }          if (listen(st, 20) == -1)          {              printf("listen failed %s\n", strerror(errno));              return EXIT_FAILURE;          }          printf("listen success\n");          int client_st = 0;          struct sockaddr_in client_addr;        pthread_t thrd1, thrd2;          while (1)          {              memset(&client_addr, 0, sizeof(client_addr));              socklen_t len = sizeof(client_addr);          printf("waiting for client.......\n");            client_st = accept(st, (struct sockaddr*) &client_addr, &len);              if (client_st == -1)              {                  printf("accept failed %s\n", strerror(errno));                  return EXIT_FAILURE;              }              printf("accept by %s\n", inet_ntoa(client_addr.sin_addr));              pthread_create(&thrd1, NULL, recvsocket, &client_st);              pthread_create(&thrd2, NULL, sendsocket, &client_st);          }          close(st);          return 0;      }

客户端 client.c

    #include <stdio.h>      #include <stdlib.h>      #include <string.h>      #include <unistd.h>      #include <errno.h>      #include <sys/types.h>      #include <sys/socket.h>      #include <netinet/in.h>      #include <arpa/inet.h>      #include <pthread.h>      void* recvsocket(void *ptr)      {          int fd = *(int *)ptr;          char str[1024];          while (1)          {              memset(str, 0, sizeof(str));              int numbytes = recv(fd, s, sizeof(str), 0);              if (numbytes <= 0)                  break;              printf("%s\n", str);          }          return NULL;      }      void* sendsocket(void *ptr)      {          int fd = *(int *)ptr;          char str[1024];          while (1)          {              memset(s, 0, sizeof(str));              read(STDIN_FILENO, str, sizeof(str));              send(fd, str, strlen(str), 0);          }          return NULL;      }      int main(int arg, char *args[])      {          int port = 1234;          int st = socket(AF_INET, SOCK_STREAM, 0);     int opt = SO_REUSEADDR;    setsockopt(st, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));        struct sockaddr_in addr;         memset(&addr, 0, sizeof(addr));          addr.sin_family = AF_INET;         addr.sin_port = htons(port);          addr.sin_addr.s_addr = htonl(INADDR_ANY);         if (bind(st, (struct sockaddr *) &addr, sizeof(addr)) == -1)          {              printf("bind failed %s\n", strerror(errno));              return EXIT_FAILURE;          }          if (listen(st, 20) == -1)          {              printf("listen failed %s\n", strerror(errno));              return EXIT_FAILURE;          }          printf("listen success\n");          int client_st = 0;          struct sockaddr_in client_addr;        pthread_t thrd1, thrd2;          while (1)          {              memset(&client_addr, 0, sizeof(client_addr));              socklen_t len = sizeof(client_addr);          printf("waiting for client.......\n");            client_st = accept(st, (struct sockaddr*) &client_addr, &len);              if (client_st == -1)              {                  printf("accept failed %s\n", strerror(errno));                  return EXIT_FAILURE;              }              printf("accept by %s\n", inet_ntoa(client_addr.sin_addr));              pthread_create(&thrd1, NULL, recvsocket, &client_st);              pthread_create(&thrd2, NULL, sendsocket, &client_st);          }          close(st);          return 0;      }

创建两个线程并发、并行地工作，分别进行发送/接收数据，（其实仅用创建一个线程，在主线程也可以完成相应的发送和接收），但是这样也有一个缺点，那就是如果要在异步通信程序上扩展其他的功能，那么接收数据的工作最好全部由接收数据的线程来完成，因为如果在其他线程中加入recv语句接收数据，那么线程之间会争抢资源，这样就无法判断是哪一个线程接收到了数据。

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