linux中select网络通信

//ser.cpp
#include <iostream>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#include <string.h>
#define IP "127.0.0.1"
#define PORT 8888
using namespace std;

int main()
{
    int sockSer,sockCli;
    sockaddr_in addrSer,addrCli;
    sockSer = socket(AF_INET,SOCK_STREAM,0);
    bzero(&addrSer,sizeof(addrSer));
    bzero(&addrCli,sizeof(addrSer));

    addrSer.sin_family = AF_INET;
    addrSer.sin_port = htons(PORT);
    addrSer.sin_addr.s_addr = inet_addr(IP);

    socklen_t len = sizeof(sockaddr_in);
    bind(sockSer,(sockaddr*)&addrSer,len);
    listen(sockSer,5);

    char clibuff[255];
    memset(clibuff,0,sizeof(clibuff));

//////////////////////////////////////////////////////

fd_set Read;
fd_set Write;
static int maxfd = 0;

int sock_set[100];//socket set.
int size = 1;//index

sockCli = accept(sockSer,(sockaddr*)&addrCli,&len); 
if(sockCli<0)
{
    cout<<sockCli<<endl;
    cout<<"accept() error!!!!"<<endl;
    close(sockSer);
    close(sockCli);
    return -1;
}
struct timeval _timeout={3,0};
off_t fd = open("a",O_CREAT|O_RDWR);
while(1)
{
 FD_ZERO(&Read);
 FD_SET(sockCli,&Read);

 FD_ZERO(&Write);
 FD_SET(fd,&Write);

 maxfd = maxfd>sockCli?
maxfd:sockCli;
 maxfd = maxfd>fd?maxfd:fd;

 select(maxfd+1,&Read,&Write,NULL,&_timeout);
 if(FD_ISSET(sockCli,&Read))
    {
        if(fork()==0)
        {
       cout<<"return"<<endl;
         char buff[255];
         memset(buff,0,sizeof(buff));
         while(1){
         read(sockCli,buff,sizeof(buff));
         cout<<buff<<endl;
         char str[]="xiaoyanzi";
         write(sockCli,str,strlen(str)+1);
         }
        }
     }
    if(FD_ISSET(fd,&Write))
        {
            write(fd,"1234",5);
            sleep(1);
        }
}
return 0;
}

#include <iostream>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#define IP "127.0.0.1"
#define PORT 8888

using namespace std;
int main()
{
    int sockCli = socket(AF_INET,SOCK_STREAM,0);
    sockaddr_in addrSer;
    bzero(&(addrSer),sizeof(addrSer));
    addrSer.sin_family = AF_INET;
    addrSer.sin_port = htons(PORT);
    addrSer.sin_addr.s_addr = inet_addr(IP);

    socklen_t len = sizeof(sockaddr_in);

    int Ret = connect(sockCli,(sockaddr*)&addrSer,len); 
    if(Ret != 0)
    {
        close(sockCli);
        return -1;
    }
    char serbuff[]="liuhuiyan";
    char clibuff[255];
    while(1)
    {
        write(sockCli,serbuff,strlen(serbuff)+1);
        read(sockCli,clibuff,sizeof(clibuff));
    cout<<clibuff<<endl;
        sleep(1);   
    }
    return 0;
}

//Makefile
SER=ser
CLI=cli
CC=g++
Status=-g


all:$(CLI) $(SER)
.PHONY:all

$(SER):$(SER).cpp
    @$(CC) -o $@ $^ $(Status)
$(CLI):$(CLI).cpp
    @$(CC) -o $@ $^ $(Status)

.PHONY:clean
clean:
    rm -rf *.o $(SER) $(CLI)