// : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "WinSock2.h"

#define MAX_BUFFER 100

int _tmain(int argc, _TCHAR* argv[])
{
    WORD wVersionRequested;
    WSADATA wsaData;
    int len;
    SOCKADDR_IN sockSerAddr,sockClientAddr;
    char *sendbuf,*recvbuf;

    wVersionRequested=MAKEWORD(2,2);
    if(0!=WSAStartup(wVersionRequested,&wsaData))
    {
        printf("faile to connect!\n");
        return 0;
    }
    if(HIBYTE(wsaData.wVersion)!=2||LOBYTE(wsaData.wVersion)!=2)
    {
        WSACleanup();
        return 0;
    }

    SOCKET sockSer=socket(AF_INET,SOCK_STREAM,0);

    sockSerAddr.sin_addr.S_un.S_addr=htonl(INADDR_ANY);
    sockSerAddr.sin_family=AF_INET;
    sockSerAddr.sin_port=htons(3000);

    if(SOCKET_ERROR==bind(sockSer,(LPSOCKADDR)&sockSerAddr,sizeof(sockaddr_in)))
    {
        printf("faile to bind!\n");
        return 0;
    }
    if(listen(sockSer,5) ==SOCKET_ERROR)
    { 
        printf("Listen failed:%d\n", WSAGetLastError()); 
        return 0; 
    } 
    len=sizeof(sockaddr);
    sendbuf=(char*)malloc(MAX_BUFFER*sizeof(char));
    recvbuf=(char*)malloc(MAX_BUFFER*sizeof(char));
    sendbuf="welcome to china !";
    while(1)
    {
        SOCKET sockconnet=accept(sockSer,(sockaddr*)&sockClientAddr,&len);
        if(sockconnet== SOCKET_ERROR)
        { 
            printf("Accept failed:%d", WSAGetLastError()); 
            break; 
        }
        printf("sockClient IP is: %s\n",inet_ntoa(sockClientAddr.sin_addr));

        int len1=send(sockconnet,sendbuf,strlen(sendbuf)+1,0);
        if(SOCKET_ERROR==len1)
        {
            printf("send failed!\n");
            break;
        }
        else
            printf("发送的数据长度是：%d\n",len1);

        memset(recvbuf,'\0',sizeof(recvbuf));
        int len2=recv(sockconnet,recvbuf,sizeof(recvbuf),0);
        if(SOCKET_ERROR==len2)
        {   
            printf("receive error!\n");
            break;
        }
        else
            printf("接收的数据长度是：%d\n接收的数据是%s\n",len2,recvbuf);

        closesocket(sockconnet);
    }
    closesocket(sockSer);
    WSACleanup();
    system("pause");
    return 0;
}

这是客服程序

//  : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "WinSock2.h"

#define MAX_BUFFER 100

int _tmain(int argc, _TCHAR* argv[])
{
    WORD wVersionRequested;
    WSADATA wsaData;
    int result;
    SOCKADDR_IN sockSer;
    char *sendbuf,*recvbuf;

    wVersionRequested=MAKEWORD(2,2);
    if(0!=WSAStartup(wVersionRequested,&wsaData))
    { 
        printf("failed to load WinSock!\n");
        return 0;
    }
    if(HIBYTE(wsaData.wVersion)!=2||LOBYTE(wsaData.wVersion)!=2)
    {
        printf("Version Wrong!\n");
        WSACleanup();
        return 0;
    }

    SOCKET socketClient=socket(AF_INET,SOCK_STREAM,0);
    if(SOCKET_ERROR == socketClient)
    { 
        printf("Socket() error1:%d\n", WSAGetLastError()); 
        return 0; 
    }  

    sockSer.sin_addr.S_un.S_addr=inet_addr("127.0.0.1");
    sockSer.sin_family=AF_INET;
    sockSer.sin_port=htons(3000);

    recvbuf=(char*)malloc(MAX_BUFFER*sizeof(char));
    sendbuf=(char*)malloc(MAX_BUFFER*sizeof(char));
    sendbuf="thank you very much !";

    if(connect(socketClient,(LPSOCKADDR)&sockSer,sizeof(sockaddr_in)))
    {
        printf("Socket() error2:%d\n", WSAGetLastError()); 
        return 0;
    }
    else
    {
        memset(recvbuf,'\0',sizeof(recvbuf));
        int len1=recv(socketClient,recvbuf,sizeof(recvbuf),0);
        if(SOCKET_ERROR==len1)
            printf("receive error!\n");
        else
             printf("接收到的数据长度是：%d\n收到的数据是：%s\n",len1,recvbuf);
        int len2=send(socketClient,sendbuf,strlen(sendbuf)+1,0);
        if(SOCKET_ERROR==len2)
            printf("send error!\n");
        else
            printf("发送的长度是：%d\n",len2);
    }
    closesocket(socketClient);
    WSACleanup();

    return 0;
}

自顶！   坐等大神！

问题太多了。
先查查sizeof是怎么用的？sizeof(指针)等于多少？
两段代码中都有，用printf把sizeof(recvbuf)的结果打印出来看看等于多少！
memset(recvbuf,'\0',sizeof(recvbuf));
int len2=recv(sockconnet,recvbuf,sizeof(recvbuf),0);

memset(recvbuf,'\0',sizeof(recvbuf));
int len1=recv(socketClient,recvbuf,sizeof(recvbuf),0);

谢谢您 ，我明白了 这求的是指针变量的长度，而不是数组的长度

自己多想想为什么自己没发现？通过调试手段能不能发现原因？

恩  谢谢您的指导，自己太想当然了没有注意到太傻了， 非常感谢！