C 实现TCP服务端（select、poll、epoll）

       使用C简单的实现一个tcp server，包括常规server、多线程实现server、select实现server、poll实现server、epoll实现server。

        IO模型原理可以看上一篇文章

#define MAXLEN 4096

int main(int argc, char **argv) {
  int listenfd, connfd, n;
  struct sockaddr_in servaddr;
  char buff[MAXLEN];

  if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
    printf("create socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }

  memset(&servaddr, 0, sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port = htons(9999);

  if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
    printf("bind socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }

  if (listen(listenfd, 10) != 0) {
    printf("listen socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }

  struct sockaddr_in client;
  socklen_t len = sizeof(client);
  if ((connfd = accept(listenfd, (struct sockaddr *)&client, &len)) == -1) {
    printf("accept socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  printf("========waiting for client's request========n");
  while (1) {
    n = recv(connfd, buff, MAXLEN, 0);
    if (n > 0) {
      buff[n] = '';
      printf("recv msg from client: %sn", buff);

      send(connfd, buff, n, 0);
    } else if (n == 0) {
      close(connfd);
    }

  close(listenfd);
  return 0;
}

        支持多个客户端并发连接。

#define MAXLEN 4096

void *client_routine(void *arg) {
  int connfd = *(int *)arg;
  char buff[MAXLEN];
  while (1) {
    int n = recv(connfd, buff, MAXLEN, 0);
    if (n > 0) {
      buff[n] = '';
      printf("recv msg from client: %sn", buff);
      send(connfd, buff, n, 0);
    } else if (n == 0) {
      close(connfd);
      break;
    }
  }
  return NULL;
}

int main(int argc, char **argv) {
  int listenfd, connfd, n;
  struct sockaddr_in servaddr;
  char buff[MAXLEN];

  if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
    printf("create socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  memset(&servaddr, 0, sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port = htons(9999);

  if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
    printf("bind socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  if (listen(listenfd, 10) != 0) {
    printf("listen socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  while (1) {
    struct sockaddr_in client;
    socklen_t len = sizeof(client);
    if ((connfd = accept(listenfd, (struct sockaddr *)&client, &len)) == -1) {
      printf("accept socket error: %s(errno: %d)n", strerror(errno), errno);
      return 0;
    }
    pthread_t threadid;
    pthread_create(&threadid, NULL, client_routine, (void *)&connfd);
  }
  close(listenfd);
  return 0;
}

        单线程支持多个客户端连接。

#define MAXLEN 4096

void *client_routine(void *arg) {
  int connfd = *(int *)arg;
  char buff[MAXLEN];
  while (1) {
    int n = recv(connfd, buff, MAXLEN, 0);
    if (n > 0) {
      buff[n] = '';
      printf("recv msg from client: %sn", buff);
      send(connfd, buff, n, 0);
    } else if (n == 0) {
      close(connfd);
      break;
    }
  }
  return NULL;
}

int main(int argc, char **argv) {
  int listenfd, connfd, n;
  struct sockaddr_in servaddr;
  char buff[MAXLEN];

  if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
    printf("create socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  memset(&servaddr, 0, sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port = htons(9999);

  if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
    printf("bind socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  if (listen(listenfd, 10) != 0) {
    printf("listen socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
fd_set rfds, rset, wfds, wset;
  FD_ZERO(&rfds);          
  FD_SET(listenfd, &rfds); 

  FD_ZERO(&wfds);

  int max_fd = listenfd;

  while (1) {
    rset = rfds;
    wset = wfds;

    int nready = select(max_fd + 1, &rset, &wset, NULL, NULL);

    
    if (FD_ISSET(listenfd, &rset)) {
      struct sockaddr_in client;
      socklen_t len = sizeof(client);
      if ((connfd = accept(listenfd, (struct sockaddr *)&client, &len)) == 1) {
        printf("accept socket error: %s(errno: %d)n", strerror(errno), errno);
        return 0;
      }

      FD_SET(connfd, &rfds);

      if (connfd > max_fd) max_fd = connfd;

      if (--nready == 0) continue;
    }

    int i = 0;
    for (i = listenfd + 1; i <= max_fd; i++) {
      if (FD_ISSET(i, &rset)) {
        n = recv(i, buff, MAXLEN, 0);
        if (n > 0) {
          buff[n] = '';
          printf("recv msg from client: %sn", buff);

          FD_SET(i, &wfds);
        } else if (n == 0) {
          FD_CLR(i, &rfds); 
          close(i);
        }
        if (--nready == 0) break;
      } else if (FD_ISSET(i, &wset)) {
        send(i, buff, n, 0);
        FD_SET(i, &rfds);
        FD_CLR(i, &wfds); 
      }
    }
  }
  close(listenfd);
  return 0;
}

#define MAXLEN 4096

void *client_routine(void *arg) {
  int connfd = *(int *)arg;
  char buff[MAXLEN];
  while (1) {
    int n = recv(connfd, buff, MAXLEN, 0);
    if (n > 0) {
      buff[n] = '';
      printf("recv msg from client: %sn", buff);
      send(connfd, buff, n, 0);
    } else if (n == 0) {
      close(connfd);
      break;
    }
  }
  return NULL;
}

int main(int argc, char **argv) {
  int listenfd, connfd, n;
  struct sockaddr_in servaddr;
  char buff[MAXLEN];

  if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
    printf("create socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  memset(&servaddr, 0, sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port = htons(9999);

  if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
    printf("bind socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  if (listen(listenfd, 10) != 0) {
    printf("listen socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
struct pollfd fds[POLL_SIZE] = {0};
  fds[0].fd = listenfd;
  fds[0].events = POLLIN;

  int max_fd = listenfd;
  int i = 0;
  for (i = 1; i < POLL_SIZE; i++) {
    fds[i].fd = -1;
  }

  while (1) {
    int nready = poll(fds, max_fd + 1, -1);
    printf("nready: %d n", nready);
    if (fds[0].revents & POLLIN) {
      struct sockaddr_in client;
      socklen_t len = sizeof(client);
      if ((connfd = accept(listenfd, (struct sockaddr *)&client, &len)) == -1) {
        printf("accept socket error: %s(errno: %d)n", strerror(errno), errno);
        return 0;
      }

      printf("accept n");
      fds[connfd].fd = connfd;
      fds[connfd].events = POLLIN;

      if (connfd > max_fd) max_fd = connfd;

      if (--nready == 0) continue;
    }

    for (i = listenfd + 1; i <= max_fd; i++) {
      if (fds[i].revents & POLLIN) {
        n = recv(i, buff, MAXLEN, 0);
        if (n > 0) {
          buff[n] = '';
          printf("recv msg from client: %sn", buff);
          fds[i].events = POLLOUT;
          // send(i, buff, n, 0);
        } else if (n == 0) {
          fds[i].fd = -1;
          close(i);
        }
        if (--nready == 0) break;
      } else if (fds[i].revents & POLLOUT) {
        send(i, buff, n, 0);
        fds[i].events = POLLIN;
      }
    }
  }
  close(listenfd);
  return 0;
}

#define MAXLEN 4096

void *client_routine(void *arg) {
  int connfd = *(int *)arg;
  char buff[MAXLEN];
  while (1) {
    int n = recv(connfd, buff, MAXLEN, 0);
    if (n > 0) {
      buff[n] = '';
      printf("recv msg from client: %sn", buff);
      send(connfd, buff, n, 0);
    } else if (n == 0) {
      close(connfd);
      break;
    }
  }
  return NULL;
}

int main(int argc, char **argv) {
  int listenfd, connfd, n;
  struct sockaddr_in servaddr;
  char buff[MAXLEN];

  if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
    printf("create socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  memset(&servaddr, 0, sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port = htons(9999);

  if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
    printf("bind socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  if (listen(listenfd, 10) != 0) {
    printf("listen socket error: %s(errno: %d)n", strerror(errno), errno);
    return 0;
  }
  int epfd = epoll_create(1);  // init size

  struct epoll_event events[POLL_SIZE] = {0};
  struct epoll_event ev;

  ev.events = EPOLLIN;
  ev.data.fd = listenfd;

  epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev);

  while (1) {
    int nready = epoll_wait(epfd, events, POLL_SIZE, 5);
    if (nready == -1) {
      continue;
    }

    int i = 0;
    for (i = 0; i < nready; i++) {
      int clientfd = events[i].data.fd;
      if (clientfd == listenfd) {
        struct sockaddr_in client;
        socklen_t len = sizeof(client);
        if ((connfd = accept(listenfd, (struct sockaddr *)&client, &len)) ==
            -1) {
          printf("accept socket error: %s(errno: %d)n", strerror(errno),
                 errno);
          return 0;
        }
        printf("acceptn");
        ev.events = EPOLLIN;
        ev.data.fd = connfd;
        epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &ev);
      } else if (events[i].events & EPOLLIN) {
        n = recv(clientfd, buff, MAXLEN, 0);
        if (n > 0) {
          buff[n] = '';
          printf("recv msg from client: %sn", buff);

          send(clientfd, buff, n, 0);
        } else if (n == 0) {
          ev.events = EPOLLIN;
          ev.data.fd = clientfd;

          epoll_ctl(epfd, EPOLL_CTL_DEL, clientfd, &ev);
          close(clientfd);
        }
      }
    }
  }
  close(listenfd);
  return 0;
}