Linux 高级I/O之poll函数及简单服务器客户端编程教程
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。
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：
<pre class="brush:cpp;toolbar:false">#include<poll.h>
int 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：
<pre class="brush:cpp;toolbar:false">#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<errno.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<pthread.h>
#include<unistd.h>
#include<poll.h>
#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：
<pre class="brush:cpp;toolbar:false">#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<errno.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#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 <ipaddress>\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：
