概念

• 這篇部落格我們利用多執行緒解決伺服器併發問題
• 程序是資源分配最小的單位，執行緒是CPU排程的最小單位
• 多程序與多執行緒比較（下圖取自網路，原作者不詳）

程式碼實現

• 伺服器端利用多執行緒程式設計
• 注意編譯的時候加上-lpthread ，否則會出現如下編譯錯誤
  

undefined reference to `pthread_create’
collect2: ld 返回 1

#include <pthread.h>
 

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void *thread_worker(void *arg);
int *p;
int main(int argc, char **argv)
{
    int                     socket_fd,  connect_fd = -1
 
;
    struct sockaddr_in      serv_addr;             
     pthread_t tid;
    socket_fd = socket(AF_INET, SOCK_STREAM, 0);
    if(socket_fd < 0 )
    {
        printf("create socket failure: %s\n", strerror(errno));
        return -1;
    }
    printf("socket create fd[%d]\n", socket_fd);

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;        
    serv_addr.sin_port = htons(9998);
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    if( bind(socket_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0 )
    {
        printf("create socket failure: %s\n", strerror(errno));
        return -2;
    }
    printf("socket bind ok\n", socket_fd);

    listen(socket_fd, 13); 
    printf("listen fd ok\n", socket_fd);

    while(1)   
    {
        printf("waiting for client's connection......\n", socket_fd);
        connect_fd = accept(socket_fd, NULL, NULL);
        p=&connect_fd;
        if(connect_fd < 0)
        {
            printf("accept new socket failure: %s\n", strerror(errno));
            return -2;
        }
        printf("accept ok, return connect_fd: [%d]\n", connect_fd);
        pthread_create (&tid, NULL,thread_worker, (void *)p);
    } 
    close(socket_fd);
}


void *thread_worker(void *arg)
{
    char                    buf[1024]; 
    int                     cli_fd =*p; 

    memset(buf, 0, sizeof(buf));        
   while(1){
    read(cli_fd, buf, sizeof(buf));     
    printf("read '%s' from client\n", buf);
    printf("send data to client:");
    fgets(buf,sizeof(buf),stdin);
    write(cli_fd, buf, strlen(buf));
    sleep(1);
    }
    close(cli_fd); 

    return NULL;
}