TCP编程：select提高服务器处理能力 [socket多路IO复用]

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/wait.h>
#include <string.h>
#include <errno.h>
#define DEFAULT_PORT 6666
int main( int argc, char ** argv){
    int serverfd,acceptfd; /* 监听socket: serverfd,数据传输socket: acceptfd */
    struct sockaddr_in my_addr; /* 本机地址信息 */
    struct sockaddr_in their_addr; /* 客户地址信息 */
    unsigned int sin_size, myport=6666, lisnum=10;
    if ((serverfd = socket(AF_INET , SOCK_STREAM, 0)) == -1) {
       perror("socket" );
       return -1;
    }
    printf("socket ok \n");
    my_addr.sin_family=AF_INET;
    my_addr.sin_port=htons(DEFAULT_PORT);
    my_addr.sin_addr.s_addr = INADDR_ANY;
    bzero(&(my_addr.sin_zero), 0);
    if (bind(serverfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr )) == -1) {
        perror("bind" );
        return -2;
    }
    printf("bind ok \n");
    if (listen(serverfd, lisnum) == -1) {
        perror("listen" );
        return -3;
    }
    printf("listen ok \n");
    
    fd_set client_fdset;    /*监控文件描述符集合*/
    int maxsock;            /*监控文件描述符中最大的文件号*/
    struct timeval tv;        /*超时返回时间*/
    int client_sockfd[5];   /*存放活动的sockfd*/
    bzero((void*)client_sockfd,sizeof(client_sockfd));
    int conn_amount = 0;    /*用来记录描述符数量*/
    maxsock = serverfd;
    char buffer[1024];
    int ret=0;
    while(1){
        /*初始化文件描述符号到集合*/
        FD_ZERO(&client_fdset);
        /*加入服务器描述符*/
    FD_SET(serverfd,&client_fdset);
    /*设置超时时间*/
    tv.tv_sec = 30; /*30秒*/
    tv.tv_usec = 0;
    /*把活动的句柄加入到文件描述符中*/
    for(int i = 0; i < 5; ++i){
/*程序中Listen中参数设为5,故i必须小于5*/
        if(client_sockfd[i] != 0){
            FD_SET(client_sockfd[i], &client_fdset);
        }
     }
    /*printf("put sockfd in fdset!\n");*/
    /*select函数*/
    ret = select(maxsock+1, &client_fdset, NULL, NULL, &tv);
    if(ret < 0){
        perror("select error!\n");
        break;
    }
    else if(ret == 0){
        printf("timeout!\n");
        continue;
    }
    /*轮询各个文件描述符*/
    for(int i = 0; i < conn_amount; ++i){
    /*FD_ISSET检查client_sockfd是否可读写，>0可读写*/
        if(FD_ISSET(client_sockfd[i], &client_fdset)){
            printf("start recv from client[%d]:\n",i);
            ret = recv(client_sockfd[i], buffer, 1024, 0);
            if(ret <= 0){
            printf("client[%d] close\n", i);
            close(client_sockfd[i]);
            FD_CLR(client_sockfd[i], &client_fdset);
            client_sockfd[i] = 0;
            }
            else{
         printf("recv from client[%d] :%s\n", i, buffer);
            }
        }
    }
    /*检查是否有新的连接，如果收，接收连接，加入到client_sockfd中*/
    if(FD_ISSET(serverfd, &client_fdset)){
        /*接受连接*/
        struct sockaddr_in client_addr;
        size_t size = sizeof(struct sockaddr_in);
int sock_client = accept(serverfd, (struct sockaddr*)(&client_addr), (unsigned int*)(&size));
if(sock_client < 0){
    perror("accept error!\n");
    continue;
}
/*把连接加入到文件描述符集合中*/
if(conn_amount < 5){
    client_sockfd[conn_amount++] = sock_client;
    bzero(buffer,1024);
    strcpy(buffer, "this is server! welcome!\n");
    send(sock_client, buffer, 1024, 0);
    printf("new connection client[%d] %s:%d\n", conn_amount, inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
    bzero(buffer,sizeof(buffer));
    ret = recv(sock_client, buffer, 1024, 0);
    if(ret < 0){
        perror("recv error!\n");
        close(serverfd);
        return -1;
    }
    printf("recv : %s\n",buffer);
    if(sock_client > maxsock){
        maxsock = sock_client;
    }
    else{
        printf("max connections!!!quit!!\n");
        break;
    }
   }
  }
}
for(int i = 0; i < 5; ++i){
    if(client_sockfd[i] != 0){
        close(client_sockfd[i]);
    }
}
close(serverfd);
return 0;    
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#define DEFAULT_PORT 6666
int main( int argc, char * argv[]){
int connfd = 0;
int cLen = 0;
struct sockaddr_in client;
if(argc < 2){
printf(" Uasge: clientent [server IP address]\n");
return -1;
}    
client.sin_family = AF_INET;
client.sin_port = htons(DEFAULT_PORT);
client.sin_addr.s_addr = inet_addr(argv[1]);
connfd = socket(AF_INET, SOCK_STREAM, 0);
if(connfd < 0){
perror("socket" );
return -1;
}
if(connect(connfd, (struct sockaddr*)&client, sizeof(client)) < 0){
perror("connect" );
return -1;
}
char buffer[1024];
bzero(buffer,sizeof(buffer));
recv(connfd, buffer, 1024, 0);
printf("recv : %s\n", buffer);
bzero(buffer,sizeof(buffer));
strcpy(buffer,"this is client!\n");
send(connfd, buffer, 1024, 0);
while(1){
bzero(buffer,sizeof(buffer));
scanf("%s",buffer);
int p = strlen(buffer);
buffer[p] = ‘\0‘;
send(connfd, buffer, 1024, 0);
printf("i have send buffer\n");
}
close(connfd);
return 0;
}