模仿pgpoolII的方式，建立线程池

接上一篇，pgpool-II中是如何实现进程池的，自己实现线程池。可以正常运行。

server端代码：con-server03.c

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

#define HELLO_WORLD_SERVER_PORT    6666
#define LENGTH_OF_LISTEN_QUEUE 20
#define BUFFER_SIZE 1024

int main(int argc, char **argv){
 struct sockaddr_in server_addr;
 bzero(&server_addr,sizeof(server_addr));
 server_addr.sin_family = AF_INET;
 server_addr.sin_addr.s_addr = htons(INADDR_ANY);
 server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);

 int server_socket = socket(AF_INET,SOCK_STREAM,0);
 if( server_socket < 0){
        printf("Create Socket Failed!");
        exit(1);
 }

if( bind(server_socket,(struct sockaddr*)&server_addr,sizeof(server_addr))){
        printf("Server Bind Port : %d Failed!", HELLO_WORLD_SERVER_PORT);
        exit(1);
}

if ( listen(server_socket, LENGTH_OF_LISTEN_QUEUE) ){
        printf("Server Listen Failed!");
        exit(1);
}

//prepare for forking children
struct sockaddr_in client_addr;
socklen_t length = sizeof(client_addr);
int procnt;
int fds;
fd_set  readmask;
int newsock;
int fd = 0;

for (procnt=0; procnt<10; procnt++){
 int child_process_pid = fork(); 

 if(child_process_pid == 0 ){
   fprintf(stderr,"Child %d is born.\n",getpid());

    while(1){
     FD_ZERO(&readmask);
     FD_SET(server_socket, &readmask);

     struct timeval timeout;
     timeout.tv_sec=30;
     timeout.tv_usec=0;
     
     int ssocket=server_socket+1;
     fds = select( ssocket, &readmask, NULL, NULL,&timeout);

     /* timeout */
     if (fds == 0){
       sleep(5);
       continue;
     }

     if (FD_ISSET(server_socket, &readmask)){
       fd =server_socket;
     }
     memset( &client_addr, 0, sizeof(client_addr));

     newsock = accept(fd, (struct sockaddr *)&client_addr, &length);

     char buffer[BUFFER_SIZE];
     bzero(buffer, BUFFER_SIZE);
     strcpy(buffer,"Hello,World! FromServer! ");
     int pd;
     pd=getpid();
     char cpd[10];
     sprintf(cpd,"%d",pd);
     strcat(buffer,cpd);
     strcat(buffer,"\n");

     send(newsock,buffer,BUFFER_SIZE,0);
            
     bzero(buffer,BUFFER_SIZE);
     length = recv(newsock,buffer,BUFFER_SIZE,0);

     if (length < 0){
                printf("Server Recieve Data Failed!\n");
                exit(1);
       }

       fprintf(stderr,"got: %s in %d\n",buffer,getpid());
       close(newsock);
   }///while circle ends

   exit(0);///child ends.never goes here

  }else{
    //parent process, do nothing
  }
} /// for circle of forking ends

for(;;){
  sleep(10);
  fprintf(stderr,"I am main process waked from sleep.\n");
}

close(server_socket);
return 0;
}

client端代码：con-client.c

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

#define HELLO_WORLD_SERVER_PORT    6666
#define BUFFER_SIZE 1024

void talk_to_server(char ** argv){
   
    struct sockaddr_in client_addr;
    bzero(&client_addr,sizeof(client_addr));
    client_addr.sin_family = AF_INET;
    client_addr.sin_addr.s_addr = htons(INADDR_ANY);
    client_addr.sin_port = htons(0);

    int client_socket = socket(AF_INET,SOCK_STREAM,0);
    if( client_socket < 0){
        printf("Create Socket Failed!\n");
        exit(1);
    }
    
    if( bind(client_socket,(struct sockaddr*)&client_addr,sizeof(client_addr))){
        printf("Client Bind Port Failed!\n");
        exit(1);
    }

    struct sockaddr_in server_addr;
    bzero(&server_addr,sizeof(server_addr));
    server_addr.sin_family = AF_INET;

    if(inet_aton(argv[1],&server_addr.sin_addr) == 0){
        printf("Server IP Address Error!\n");
        exit(1);
    }
    server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);
    socklen_t server_addr_length = sizeof(server_addr);

    if( connect( client_socket, (struct sockaddr*)&server_addr, 
          server_addr_length) < 0){
        printf("Can Not Connect To %s!\n",argv[1]);
        exit(1);
    }

    char buffer[BUFFER_SIZE];
    bzero(buffer,BUFFER_SIZE);

    int length = recv(  client_socket,  buffer,BUFFER_SIZE,0);
    if(length < 0){
        printf("Recieve Data From Server %s Failed!\n", argv[1]);
        exit(1);
    }
    printf("From Server %s :\t%s",argv[1],buffer);

    bzero(buffer,BUFFER_SIZE);
    char name[64];
    gethostname(name,sizeof(name));
    strcpy(buffer,name);
    send(client_socket,buffer,BUFFER_SIZE,0);
    close(client_socket);
}

int main(int argc, char **argv){
    if (argc != 2){
        printf("Usage: ./%s ServerIPAddress\n",argv[0]);
        exit(1);
    }

    int i=0;
    for(i=0; i<10000; i++){
        talk_to_server(argv);
        sleep(10);
    }
    return 0;
}

基本上来说，server端的实现方式，就是：

监听某个port, listen后，开始建立若干的子进程。在父进程里进入sleep/循环；

在子进程里面，select/accept ，accept后作动作，然后循环往复。

好像酒店大堂的门口，开了门纳客(监听)；

然后派一批员工(子进程)等在门口(listen/accept)，

若有客人来(网络请求)，哪个员工(子进程)逮住了就给迎进酒店，领位(服务)，然后循环往复。