这篇文章主要介绍“Linux下select异步通讯如何实现”的相关知识，小编通过实际案例向大家展示操作过程，操作方法简单快捷，实用性强，希望这篇“Linux下select异步通讯如何实现”文章能帮助大家解决问题。
1.服务器端
/*select_server.c 2011.9.2 by yyg*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <pthread.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <arpa/inet.h>
#include <unistd.h>
#define MAXBUF 1024
int main(int argc,char **argv){
int sockfd,new_fd;
socklen_t len;
struct sockaddr_in my_addr,their_addr;
unsigned int myport,lisnum;
char buf[MAXBUF+1];
fd_set rfds;
struct timeval（argv[1]){
myport = atoi(argv[1]);
}
else
myport = 7838;
if(argv[2]){
lisnum = atoi(argv[2]);
}
else
lisnum =2;
if((sockfd = socket(PF_INET,SOCK_STREAM,0))== -1){
perror("socket");
exit(1);
}
bzero(&my_addr,sizeof(my_addr));
my_addr.sin_family = PF_INET;
my_addr.sin_port = htons(myport);
if(argv[3])
my_addr.sin_addr.s_addr = INADDR_ANY;
if(bind(sockfd,(struct sockaddr *)&my_addr,sizeof(struct sockaddr)) == -1){
perror("bind");
exit(1);
}
if(listen(sockfd, lisnum) == -1){
perror("listen");
exit(1);
}
while(1){
printf("\n----waiting for new connecting to start new char----\n");
len = sizeof(struct sockaddr);
if((new_fd = accept(sockfd,(struct sockaddr *)&their_addr,&len)) == -1){
perror("accept");
exit(errno);
}
else
printf("server:got connection from %s,port %d,socked %d\n",\
inet_ntoa(their_addr.sin_addr),\
ntohs(their_addr.sin_port),new_fd);
/*开始处理每个新连接上的数据收发*/
//printf("\n---ready to go.now you can chatting...input enter,then you can chat---\n");
while(1){
/*把集合清空*/
FD_ZERO(&rfds);
/*把标准输入句柄0加入到集合中*/
FD_SET(0,&rfds);
maxfd = 0;
/*把当前连接句柄new_fd加入到集合中*/
FD_SET(new_fd,&rfds);
if(new_fd > maxfd)
maxfd = new_fd;
/*设置最大等待时间*/
tv.tv_sec = 1;
tv.tv_usec = 0;
retval = select(maxfd+1,&rfds,NULL,NULL,&tv);
if(retval == -1){
printf("select error!%s\n",strerror(errno));
break;
}
else if(retval == 0){
//printf("no message come,user no press the button,please wait...\n");
continue;
}
else{
if(FD_ISSET(new_fd,&rfds)){
/*连接的socket 上有消息则接收并显示*/
bzero(buf,MAXBUF+1);
/*接收对方发过来的消息，最多MAXBUF字节*/
len = recv(new_fd, buf, MAXBUF, 0);
if(len > 0)
printf("recv msg success:%s! %d bytes rcv.\n ",buf,len);
else{
if(len < 0){
printf("recv msg fail.the errno is:%d,error info is %s.\n",errno,strerror(errno));
}
else
printf("quit.\n");
break;
}
}// FD_ISSET = sockfd情况
if(FD_ISSET(0,&rfds)){
/*用户有输入了，则读取其内容并发送*/
bzero(buf, MAXBUF+1);
fgets(buf, MAXBUF, stdin);
if(!strncasecmp(buf, "quit", 4)){
printf("self request to quit the chating\n");
break;
}
/*发消息给服务器*/
len = send(new_fd, buf, strlen(buf)-1 , 0);
if(len < 0){
printf("mgs:%s send fail!errno is:%d,error info is:%s\n", buf, errno, strerror(errno));
break;
}else{
printf("msg: %s\t send success, send %d bytes!\n", buf, len);
}
}//FD_ISSET = 0
}//select 处理结束
}/*内while*/
close(new_fd);
/*处理每个新连接上的数据收发结束*/
printf("would you want to chatting with another one?(no->quit)");
fflush(stdout);
bzero(buf,MAXBUF+1);
fgets(buf,MAXBUF,stdin);
if(!strncasecmp(buf,"no",2)){
printf("quit the chatting!\n");
break;
}
}/*外while*/
close(sockfd);
return 0;
}2.客户端
/*select_client.c 2011.9.2 by yyg*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <pthread.h>
#include <sys/time.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <resolv.h>
#define MAXBUF 1024
int main(int argc,char **argv){
int sockfd,len;
struct sockaddr_in dest;
char buffer[MAXBUF+1];
fd_set rfds;
struct timeval（argc != 3){
printf("the param style wrong!\n");
exit(0);
}
/*创建一个socket用于tcp通信*/
if((sockfd = socket(AF_INET,SOCK_STREAM,0)) < 0){
perror("socket");
exit(errno);
}
/*初始化服务器端(对方)的地址和端口信息*/
bzero(&dest,sizeof(dest));
dest.sin_family = AF_INET;
dest.sin_port = htons(atoi(argv[2]));
if(inet_aton(argv[1],(struct in_addr *)&dest.sin_addr.s_addr) == 0){
perror(argv[1]);
exit(errno);
}
/*conect to the server*/
if(connect(sockfd,(struct sockaddr*)&dest,sizeof(dest)) !=0){
perror("connect");
exit(errno);
}
printf("\n---ready to chatting...---\n");
while(1){
/*把集合清空*/
FD_ZERO(&rfds);
/*把标准输入句柄0加入到集合中*/
FD_SET(0,&rfds);
maxfd = 0;
/*把当前连接句柄socket 加入到集合中*/
FD_SET(sockfd,&rfds);
if(sockfd > maxfd)
maxfd = sockfd;
/*设置最大等待时间*/
tv.tv_sec = 1;
tv.tv_usec = 0;
/*开始等待*/
retval = select(maxfd+1,&rfds,NULL,NULL,&tv);
if(retval == -1){
printf("select error,quit!\n");
break;
}else if(retval == 0){
continue;
}else{
if(FD_ISSET(sockfd,&rfds)){
/*连接的socket 上有消息则接收并显示*/
bzero(buffer,MAXBUF+1);
/*接收对方发过来的消息，最多MAXBUF字节*/
len = recv(sockfd, buffer, MAXBUF, 0);
if(len > 0)
printf("recv msg success:%s! %d bytes rcv.\n ",buffer,len);
else{
if(len < 0){
printf("recv msg fail.the errno is:%d,error info is %s.\n",errno,strerror(errno));
}
else
printf("quit.\n");
break;
}
}// FD_ISSET = sockfd情况
if(FD_ISSET(0,&rfds)){
/*用户有输入了，则读取其内容并发送*/
bzero(buffer, MAXBUF+1);
fgets(buffer, MAXBUF, stdin);
if(!strncasecmp(buffer, "quit", 4)){
printf("self request to quit the chating\n");
break;
}
/*发消息给服务器*/
len = send(sockfd, buffer, strlen(buffer)-1 , 0);
if(len < 0){
printf("mgs:%s send fail!errno is:%d,error info is:%s\n", buffer, errno, strerror(errno));
break;
}else{
printf("msg: %s\t send success, send %d bytes!\n", buffer, len);
}
}//FD_ISSET = 0
}//select 处理结束
}//处理聊天的while 循环
/*关闭连接*/
close(sockfd);
return 0;
}运行结果：
终端1：服务器端
[root@localhost net]# ./select_server 7838 ----waiting for new connecting to start new char---- server:got connection from 172.31.100.236,port 59462,socked 4 recv msg success:kfldsjfk! 8 bytes rcv. 456354 msg: 456354 send success, send 6 bytes! recv msg success:453455! 6 bytes rcv.
终端2：客户端
[root@localhost net]# ./select_client 172.31.100.236 7838 ---ready to chatting...--- kfldsjfk msg: kfldsjfk send success, send 8 bytes! recv msg success:456354! 6 bytes rcv. 453455 msg: 453455 send success, send 6 bytes!
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