Linux I/O multiplexing--poll ()

1, poll ()

The poll () system call is similar to select () and also polls a certain number of file descriptors to test if they have a ready person.

API functions:

int poll (struct POLLFD *fds, nfds_t nfds, int timeout);

Parameters: nfds+1;

struct POLLFD {
int FD; /* File Descriptor */
Short events; /* Requested Events */
Short revents; /* Returned events */
};

where the FD member is the specified file descriptor, the events member tells poll which events to listen on, and Revents is modified by the kernel.

There are some macros as auxiliary event parameters;

2. Code implementation

(1), utili.h

#include <unistd.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys /socket.h> #include <arpa/inet.h> #include <netinet/in.h> #include <assert.h> #include <sys/ select.h> #define SERVER_IP "127.0.0.1" #define Server_port 8787#define listen_queue 5#define SIZE 10#define buffer_ SIZE 256#include<poll.h> #define OPEN_MAX 1000

(2), ser.c

#include ". /utili.h "Static int socket_bind (const char *ip, int port) {     int listenfd = socket (af_inet, sock_stream, 0);     struct  sockaddr_in addrSer;    addrSer.sin_family = AF_INET;   &NBSP;&NBSP;//ADDRSER.SIN_ADDR.S_ADDR&NBSP;=&NBSP;INET_ADDR (IP);     inet_pton (AF_INET, &NBSP;IP,&NBSP;&AMP;ADDRSER.SIN_ADDR);     addrser.sin_port = htons (port);     bind (listenfd,  (struct sockaddr*) &addrser, sizeof (STRUCT&NBSP;SOCKADDR)); &NBSP;&NBSP;&NBSP;&NBSP;RETURN&NBSP;LISTENFD;} Static void handle_connection (Struct pollfd *connfds, int num) {     char buffer[buffer_size];    int i;    for (I=1;  i<=num; ++i) {        if (CONNFDS[I].FD&NBSP;==&NBSP;-1)              continue ;         if (Connfds[i].revents & pollin) {   &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;RECV (Connfds[i].fd, buffer, buffer_size,  0);              printf ("Server  Accept client msg:>%s\n ", buffer);             send (Connfds[i].fd, buffer, strlen (buffer) +1, 0);          }       }   }static void  Do_poll (INT&NBSP;LISTENFD) {    struct sockaddr_in addrcli;     int connfd;    struct pollfd clientfds[OPEN_MAX];     clientfds[0].fd = listenfd;    clientfds[0].events = pollin;    int i;     for (i=1; i<open_max; ++i) {         clientfds[i].fd = -1;    }    int nready;     int max = 0;    for (;;) {        nready = poll (clientfds, max+1, -1);         if (nready == -1) {             perror ("poll");             return;        }         if (nready == 0) {             printf ("server wait time out.\n");             continue;         }        if (Clientfds[0].revents & pollin) {             socklen_t len = sizeof ( STRUCT&NBSP;SOCKADDR);             connfd =  accept (listenfd,  (struct sockaddr*) &addrcli, &len);             int i;             for (i=1; i<open_max; ++i) {                 if (clientfds[i].fd == -1) {                     clientfds[i]. fd = connfd;                     break;                }             }             if (I == open_max) {                 printf ("over load.\n");                 exit (1);             }             clientfds[i].events = POLLIN;             max =  (I>max ? i : max);         }   &nbSp;    handle_connection (Clientfds, max);     }}int main (void ) {    int listenfd;    listenfd = socket_bind (SERVER_IP ,  server_port);     listen (listenfd, listen_queue);     do_ Poll (LISTENFD);     return 0;}

(3), CLI.C

#include ". /utili.h "Static void handle_connection (INT SOCKFD) {    STRUCT POLLFD  pfds[2];    pfds[0].fd = sockfd;    pfds[0].events  = pollin;    pfds[1].fd = stdin_fileno;    pfds[1 ].events = pollin;    char buffer[buffer_size];    for ( ;;) {        poll (pfds, 2, -1);   //-1 means never timeout          if (Pfds[0].revents & pollin) {             RECV (sockfd, buffer, buffer_size, 0);              printf ("msg:> %s\n", buffer);         }            if (pfds[1].revents & pollin) {             scanf ("%s",  buffer);             //read (STDIN_ Fileno, buffer, buffer_size);             send (Sockfd, buffer, strlen (buffer) +1, 0);          }       }   }int main (void) {     int sockfd = socket (af_inet, sock_stream, 0);      struct sockaddr_in addrSer;    addrSer.sin_family = AF_INET;     addrser.sin_port = htons (server_port);     addrser.sin_ ADDR.S_ADDR = INET_ADDR (SERVER_IP);     connect (sockfd,  (struct  sockaddr*) &addrser, sizeof (STRUCT SOCKADDR));     handle_connection (SOCKFD);     return 0;} 

Run results

Server-side

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Client 1

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Client 2

650) this.width=650; "Src=" Http://s4.51cto.com/wyfs02/M01/88/19/wKiom1fpUoCjyuP_AAAkjmdZIgc333.png-wh_500x0-wm_3 -wmp_4-s_991912699.png "title=" Qq20160927005303.png "alt=" Wkiom1fpuocjyup_aaakjmdzigc333.png-wh_50 "/>

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Linux I/O multiplexing--poll ()