TCP之简单回传（二）

鉴于TCP之简单回传（一）   中所出现的问题，本博文所要采取的一种方法是：

客户端：先向服务器传送一个 int32_t 大小的数据，表示随后所要发送数据的真实长度； 

服务器：先接收一个int32_t 大小的数据，再接收真实的数据；

本程序中所用到的函数都可以在 TCP之函数封装 中找到；

server服务器端具体实现： 

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define ERR_EXIT(m) 
    do { 
        perror(m);
        exit(EXIT_FAILURE);
    }while(0)

void do_server(int fd);

int main(int argc, const char *argv[])
{
//socket    
    int listenfd = socket(AF_INET, SOCK_STREAM, 0 );
    if( -1 == listenfd)
        ERR_EXIT("socket");
//地址复用
    int on = 1;
    if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof on) < 0)
        ERR_EXIT("setsockopt");
//bind
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8888); //主机字节序转化为网络字节序
    addr.sin_addr.s_addr = inet_addr("127.0.0.1");//点分十进制转化成网络字节序
    if( -1 == bind( listenfd, (struct sockaddr*)&addr, sizeof(addr)))
        ERR_EXIT("bind");

//listen
    if( -1 == listen(listenfd,SOMAXCONN ))
        ERR_EXIT("listen");
    
//accept    
    int peerfd = accept(listenfd, NULL, NULL);//对方的IP&PORT

//read&write    
    do_server(peerfd);

//close
    close(peerfd);
    close(listenfd);
    return 0;
}

void do_server(int  fd)
{
    char recvbuf[1024100] = {0};
    int cnt =0;
    while(1)
    {
        int32_t len = recv_int32(fd);//先接收一个表示真是长度的int型数据    
        int nread = readn(fd, recvbuf, len);//读取数据
        if(nread == -1)//err
        {
            if(errno == EINTR)
                continue;
            ERR_EXIT("read");
        }else if (nread == 0 || nread < len )//write close
        {
            printf("close...
");
            exit(EXIT_FAILURE);
        }
        
        // ok 
        printf("count = %d recv size = %d
",++cnt, nread);
        memset(recvbuf, 0, sizeof(recvbuf));
    }
}

client客户端具体实现：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define ERR_EXIT(m) 
    do { 
        perror(m);
        exit(EXIT_FAILURE);
    }while(0)
void do_server(int fd);

int main(int argc, const char *argv[])
{
//socket
    int peerfd = socket(AF_INET, SOCK_STREAM,0);
    if( -1 == peerfd)
        ERR_EXIT("socket");
//connect
    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8888);
    addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    
    if( -1 == connect(peerfd,(struct sockaddr*)&addr, sizeof(addr) ))
        ERR_EXIT("connect");

//read&write
    do_server(peerfd);

    return 0;
}

void do_server(int fd)
{
    #define SIZE 1024
    char sendbuf[SIZE +1]= {0};
    int i ;
    for (i = 0; i < SIZE; i++) 
    {
        sendbuf[i]= 'a';    
    }
    int cnt =0;
    while(1)
    {
        int i;
        for (i = 0; i < 10; i++) 
        {
            send_int32(fd, SIZE);//先发送一个表示真实长度的int型数据
            int nwrite =writen(fd, sendbuf, SIZE);//写数据
            if( nwrite != SIZE)//err
                ERR_EXIT("writen");
            printf("cout = %d,write %d bytes
",++cnt, SIZE);
        }
        nano_sleep(4.5);
    }
}

测试结果：

./server
count = 1 recv size = 1024
count = 2 recv size = 1024
count = 3 recv size = 1024
count = 4 recv size = 1024
count = 5 recv size = 1024
count = 6 recv size = 1024
count = 7 recv size = 1024
count = 8 recv size = 1024
count = 9 recv size = 1024
count = 10 recv size = 1024
count = 11 recv size = 1024
count = 12 recv size = 1024
count = 13 recv size = 1024
count = 14 recv size = 1024
count = 15 recv size = 1024
count = 16 recv size = 1024
count = 17 recv size = 1024
count = 18 recv size = 1024
count = 19 recv size = 1024
count = 20 recv size = 1024

./client
cout = 1,write 1024 bytes
cout = 2,write 1024 bytes
cout = 3,write 1024 bytes
cout = 4,write 1024 bytes
cout = 5,write 1024 bytes
cout = 6,write 1024 bytes
cout = 7,write 1024 bytes
cout = 8,write 1024 bytes
cout = 9,write 1024 bytes
cout = 10,write 1024 bytes
cout = 11,write 1024 bytes
cout = 12,write 1024 bytes
cout = 13,write 1024 bytes
cout = 14,write 1024 bytes
cout = 15,write 1024 bytes
cout = 16,write 1024 bytes
cout = 17,write 1024 bytes
cout = 18,write 1024 bytes
cout = 19,write 1024 bytes
cout = 20,write 1024 bytes