UDP并发服务器简单示例

并发服务器的思想是每一个客户的请求并不由服务器直接处理，而是由服务器创建一个子进程来处理

1. 服务器端

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>
#include <netdb.h>
#include <pthread.h>

//线程执行函数负责读写
void *thr_fn(void *arg)
{
    int size, j;
    char recv_buf[1024];
    int *parg = (int *)arg;
    int new_fd = *parg;
    
    printf("new_fd = %d\n", new_fd);
    
    while((size=read(new_fd, recv_buf, 1024)) > 0)
    {
        if(recv_buf[0]=='@')
            break;
        printf("Message from client(%d): %s\n",size,recv_buf);
        for(j = 0; j < size; j++)
            recv_buf[j] = toupper(recv_buf[j]);
        write(new_fd, recv_buf, size);
    }
    
    close(new_fd);
    
    return 0;
}


int main(int argc,char *argv[])
{
    socklen_t clt_addr_len;
    int listen_fd;
    int com_fd;
    int ret;
    int i;
    static char recv_buf[1024];
    int len;
    int port;
    pthread_t tid;

    struct sockaddr_in clt_addr;
    struct sockaddr_in srv_addr;

    //服务器端运行时要给出端口信息，该端口为监听端口 
    if(argc != 2)
    {
        printf("Usage:%s port\n", argv[0]);
        return 1;
    }

    //获得输入的端口 
    port = atoi(argv[1]);

    //创建套接字用于服务器的监听 
    listen_fd = socket(PF_INET, SOCK_STREAM, 0);
    if(listen_fd < 0)
    {
        perror("cannot create listening socket");
        return 1;
    }

    //填充关于服务器的套节字信息
    memset(&srv_addr, 0, sizeof(srv_addr));
    
    srv_addr.sin_family = AF_INET;
    srv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    srv_addr.sin_port = htons(port);


    //将服务器和套节字绑定
    ret = bind(listen_fd, (struct sockaddr *)&srv_addr, sizeof(srv_addr));
    if(ret == -1)
    {
        perror("cannot bind server socket");
        close(listen_fd);
        return 1;
    }

    //监听指定端口，连接5个客户端 
    ret = listen(listen_fd, 5);
    if(ret == -1)
    {
        perror("cannot listen the client connect request");
        close(listen_fd);
        return 1;
    }
    //对每个连接来的客户端创建一个线程，单独与其进行通信 
    //首先调用read函数读取客户端发送来的信息 
    //将其转换成大写后发送回客户端 
    //当输入“@”时，程序退出 
    while(1)
    {
        len = sizeof(clt_addr);
        
        com_fd = accept(listen_fd, (struct sockaddr *)&clt_addr, &len);
        if(com_fd < 0)
        {
            if(errno == EINTR)
            {
                continue;
            }
            else
            {
                perror("cannot accept client connect request");
                close(listen_fd);
                
                return 1;
            }
        }
        
        printf("com_fd = %d\n", com_fd);//打印建立连接的客户端产生的套节字
        if((pthread_create(&tid, NULL, thr_fn, &com_fd)) == -1)
        {
            perror("pthread_create error");
            close(listen_fd);
            close(com_fd);
            
            return 1;
        }
    }
    
    return 0;
}

2. 客户端

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <netdb.h>
#include <unistd.h>

int main(int argc,char *argv[])
{
    int connect_fd;
    int ret;
    char snd_buf[1024];
    int i;
    int port;
    int len;

    static struct sockaddr_in srv_addr;

    //客户端运行需要给出具体的连接地址和端口 
    if(argc != 3)
    {
        printf("Usage: %s server_ip_address port\n",argv[0]);
        return 1;
    }

    //获得输入的端口
    port = atoi(argv[2]);

    //创建套节字用于客户端的连接
    connect_fd = socket(PF_INET,SOCK_STREAM,0);
    if(connect_fd < 0)
    {
        perror("cannot create communication socket");
        return 1;
    }

    //填充关于服务器的套节字信息
    memset(&srv_addr, 0, sizeof(srv_addr));
    
    srv_addr.sin_family = AF_INET;
    srv_addr.sin_addr.s_addr = inet_addr(argv[1]);
    srv_addr.sin_port = htons(port);

    //连接指定的服务器 
    ret = connect(connect_fd, (struct sockaddr *)&srv_addr, sizeof(srv_addr));
    if(ret == -1)
    {
        perror("cannot connect to the server");
        close(connect_fd);
        return 1;
    }

    memset(snd_buf, 0, 1024);
    //用户输入信息后，程序将输入的信息通过套接字发送给服务器 
    //然后调用read函数从服务器中读取发送来的信息 
    //当输入“@”时，程序退出 
    while(1)
    {
        write(STDOUT_FILENO, "input message:", 14);
        len = read(STDIN_FILENO, snd_buf, 1024);
        if(len > 0)
            write(connect_fd, snd_buf, len);
        len = read(connect_fd, snd_buf, len);
        if(len > 0)
            printf("Message form server: %s\n", snd_buf);
        if(snd_buf[0] == '@')
            break;
    }
    
    close(connect_fd);
    
    return 0;
}