IO多路复用之select全面总结(必看篇)

客户端程序如下：

#include <netinet/in.h>
#include <sys/socket.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/select.h>
#include <time.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>

#define MAXLINE 1024
#define IPADDRESS "127.0.0.1"
#define SERV_PORT 8787

#define max(a,b) (a > b) ? a : b

static void handle_recv_msg(int sockfd, char *buf) 
{
printf("client recv msg is:%sn", buf);
sleep(5);
write(sockfd, buf, strlen(buf) +1);
}

static void handle_connection(int sockfd)
{
char sendline[MAXLINE],recvline[MAXLINE];
int maxfdp,stdineof;
fd_set readfds;
int n;
struct timeval tv;
int retval = 0;

while (1) {

FD_ZERO(&readfds);
FD_SET(sockfd,&readfds);
maxfdp = sockfd;

tv.tv_sec = 5;
tv.tv_usec = 0;

retval = select(maxfdp+1,&readfds,NULL,NULL,&tv);

if (retval == -1) {
return ;
}

if (retval == 0) {
printf("client timeout.n");
continue;
}

if (FD_ISSET(sockfd, &readfds)) {
n = read(sockfd,recvline,MAXLINE);
if (n <= 0) {
fprintf(stderr,"client: server is closed.n");
close(sockfd);
FD_CLR(sockfd,&readfds);
return;
}

handle_recv_msg(sockfd, recvline);
}
}
}

int main(int argc,char *argv[])
{
int sockfd;
struct sockaddr_in servaddr;

sockfd = socket(AF_INET,SOCK_STREAM,0);

bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
inet_pton(AF_INET,IPADDRESS,&servaddr.sin_addr);

int retval = 0;
retval = connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr));
if (retval < 0) {
fprintf(stderr, "connect fail,error:%sn", strerror(errno));
return -1;
}

printf("client send to server .n");
write(sockfd, "hello server", 32);

handle_connection(sockfd);

return 0;
}

4、程序结果

启动服务程序，执行三个个客户程序进行测试，结果如下图所示：

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