Linux高级I/O之poll函数及简单服务器客户端编程
当需要同时监听多个文件描述符时，就需要I/O复用函数，I/O复用函数有select、poll、epoll，今天主要使用poll函数。
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poll()接受一个指向结构'struct pollfd'列表的指针，其中包括了你想测试的文件描述符和事件。事件由一个在结构中事件域的比特掩码确定。当前的结构在调用后将被填写并在事件发生后返回。
函数原型：
#includeint poll(struct pollfd *fds, nfds_t nfds, int timeout); struct pollfd{ int fd; /*file descriptor*/ short events; /*requested events*/ short revents; /*returned events*/ }
函数参数：fds是要监听的fd的数组，nfds是数组个数，timeout 超时时间 -1是阻塞；
函数说用：通过传入的events的类型去判断返回的类型是否一致，如果一致就该干事了。
events：
常量 | 说明 |
POLLIN | 普通或优先级带数据可读 |
POLLRDNORM | 普通数据可读 |
POLLRDBAND | 优先级带数据可读 |
POLLPRI | 高优先级数据可读 |
POLLOUT | 普通数据可写 |
POLLWRNORM | 普通数据可写 |
POLLWRBAND | 优先级带数据可写 |
POLLERR | 发生错误 |
POLLHUP | 发生挂起 |
POLLNVAL | 描述字不是一个打开的文件 |
接下来是是一个服务器监听两个socket的例子：
服务器代码：
#include#include #include #include #include #include #include #include #include #include #define MAX_POLLFD_NUM 2 //#define SERVER_CONN_IP1 "1.1.1.1" //#define SERVER_CONN_IP2 "1.1.1.1" #define DEFAULT_PORT 8000 #define BUFF_MAX 1024 typedef void(*Server_Rrocess_Thread_Fun)(void *arg); /*thread process function define */ typedef struct sever_thread_fun{ Server_Rrocess_Thread_Fun Server_Process_Client_Conn1; Server_Rrocess_Thread_Fun Server_Process_Client_Conn2; }Poll_Server_Process_Clinet_FUN_t; /*connect 1 thread function*/ void *Poll_Conn1_Process(void *arg) { unsigned char ucBufArr[BUFF_MAX] = {0}; unsigned long ulSize = 0; int connect_fd ; printf("come pthread conn1 fun to proess conn1\n"); if( (connect_fd = accept( *(int*)arg, (struct sockaddr*)NULL, NULL)) == -1){ printf("accept socket error: %s(errno: %d)",strerror(errno),errno); } ulSize = recv(connect_fd, ucBufArr, BUFF_MAX, 0); if(send(connect_fd, "Hello,you are connected 1!\n", 26,0) == -1) perror("send error"); ucBufArr[ulSize] = '\0'; //sleep(20); printf("recv msg from client: %s\n", ucBufArr); close(connect_fd); pthread_exit((void*)1); } /*connect 1 thread function*/ void *Poll_Conn2_Process(void *arg) { unsigned char ucBufArr[BUFF_MAX] = {0}; unsigned long ulSize = 0; int connect_fd ; printf("come pthread conn2 fun to proess conn2\n"); if( (connect_fd = accept( *(int*)arg, (struct sockaddr*)NULL, NULL)) == -1){ printf("accept socket error: %s(errno: %d)",strerror(errno),errno); } ulSize = recv(connect_fd, ucBufArr, BUFF_MAX, 0); if(send(connect_fd, "Hello,you are connected 2!\n", 26,0) == -1) perror("send error"); ucBufArr[ulSize] = '\0'; // sleep(20); printf("recv msg from client: %s\n", ucBufArr); close(connect_fd); pthread_exit((void*)2); } int main() { int poll_ret = 0; pthread_t thread_conn1; pthread_t thread_conn2; /*socket var*/ int server_socket_fd_conn1; int server_socket_fd_conn2; struct sockaddr_in servaddr_conn1; struct sockaddr_in serveraddr_conn2; /*poll var*/ struct pollfd pollfd_arr[MAX_POLLFD_NUM]; /*init thread fun*/ Poll_Server_Process_Clinet_FUN_t server_conn_handel; server_conn_handel.Server_Process_Client_Conn1 = Poll_Conn1_Process; server_conn_handel.Server_Process_Client_Conn2 = Poll_Conn2_Process; /*create two server socket*/ if( (server_socket_fd_conn1 = socket(AF_INET, SOCK_STREAM, 0)) == -1 ){ printf("create socket conn1 error: %s(errno: %d)\n",strerror(errno),errno); exit(0); } if( (server_socket_fd_conn2 = socket(AF_INET, SOCK_STREAM, 0)) == -1 ){ printf("create socket conn2 error: %s(errno: %d)\n",strerror(errno),errno); exit(0); } /*init socket 1 for conn1*/ memset(&servaddr_conn1, 0, sizeof(servaddr_conn1)); servaddr_conn1.sin_family = AF_INET; servaddr_conn1.sin_addr.s_addr = htonl(INADDR_ANY); servaddr_conn1.sin_port = htons(DEFAULT_PORT); // if( inet_pton(AF_INET, SERVER_CONN_IP1, &servaddr_conn1.sin_addr.s_addr) <= 0){ // printf("inet_pton error for %s\n",SERVER_CONN_IP1); // exit(0); // } /*init socket 2 for conn2*/ memset(&serveraddr_conn2, 0, sizeof(serveraddr_conn2)); serveraddr_conn2.sin_family = AF_INET; serveraddr_conn2.sin_addr.s_addr = htonl(INADDR_ANY); serveraddr_conn2.sin_port = htons(DEFAULT_PORT+1); // if( inet_pton(AF_INET, SERVER_CONN_IP2, &serveraddr_conn2.sin_addr.s_addr) <= 0){ // printf("inet_pton error for %s\n",SERVER_CONN_IP2); // exit(0); // } /*bind connect 1 socket*/ if( bind(server_socket_fd_conn1, (struct sockaddr*)&servaddr_conn1, sizeof(servaddr_conn1)) == -1){ printf("bind socket error1: %s(errno: %d)\n",strerror(errno),errno); exit(0); } /*bind connect 2 socket*/ if( bind(server_socket_fd_conn2, (struct sockaddr*)&serveraddr_conn2, sizeof(serveraddr_conn2)) == -1){ printf("bind socket error2: %s(errno: %d)\n",strerror(errno),errno); exit(0); } /*listen connect 1*/ if( listen(server_socket_fd_conn1, 10) == -1){ printf("listen socket error: %s(errno: %d)\n",strerror(errno),errno); exit(0); } /*listen connect 2*/ if( listen(server_socket_fd_conn2, 10) == -1){ printf("listen socket error: %s(errno: %d)\n",strerror(errno),errno); exit(0); } pollfd_arr[0].events = POLLRDNORM;/*only read event*/ pollfd_arr[0].fd = server_socket_fd_conn1; pollfd_arr[1].events = POLLRDNORM;/*only read event*/ pollfd_arr[1].fd = server_socket_fd_conn2; while(1) { poll_ret = poll( pollfd_arr, MAX_POLLFD_NUM,-1); if( pollfd_arr[0].revents & POLLRDNORM ) { /*connect 1 process task*/ pthread_create( &thread_conn1, NULL, server_conn_handel.Server_Process_Client_Conn1, (void *)(&pollfd_arr[0].fd)); } if( pollfd_arr[1].revents & POLLRDNORM ) { /*connect 2 process task*/ pthread_create( &thread_conn2, NULL, server_conn_handel.Server_Process_Client_Conn2, (void *)(&pollfd_arr[1].fd)); } sleep(1); } return 0; }
客户端代码：
#include#include #include #include #include #include #include #define BUFF_MAX 1024 #define DEFAULT_PORT 8000 int main(int argc, char** argv) { int sockfd, n,rec_len; char recvline[BUFF_MAX], sendline[BUFF_MAX]; char buf[BUFF_MAX]; struct sockaddr_in servaddr; if( argc != 2){ printf("usage: ./client \n"); exit(0); } /*create socket*/ if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){ printf("create socket error: %s(errno: %d)\n", strerror(errno),errno); exit(0); } memset(&servaddr, 0, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_port = htons(DEFAULT_PORT/*+1/);/*DEFAULT_PORT is connect 1 to server,DEFAULT_PORT+1 is connect 2 to server*/ /*string ip to int ip*/ if( inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0){ printf("inet_pton error for %s\n",argv[1]); exit(0); } /*connect server*/ if( connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0){ printf("connect error: %s(errno: %d)\n",strerror(errno),errno); exit(0); } printf("send msg to server: \n"); fgets(sendline, BUFF_MAX, stdin); /*write data to sockfd*/ if( send(sockfd, sendline, strlen(sendline), 0) < 0) { printf("send msg error: %s(errno: %d)\n", strerror(errno), errno); exit(0); } /*read socket data*/ if((rec_len = recv(sockfd, buf, BUFF_MAX,0)) == -1) { perror("recv error"); exit(1); } buf[rec_len] = '\0'; printf("Received : %s \n",buf); /*colse socket*/ close(sockfd); exit(0); }
解释：服务器端监听 ip 127.0.0.1 port 8000和ip 127.0.0.1 port 8001
结果演示：
本文标题：Linux高级I/O之poll函数及简单服务器客户端编程
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