C++ Linux网络编程，超简单的例子，就是不知道什么原因，客户端收不到消息

Question

综述：就是客户端和服务端的一次通信，但是总也运行不到预期的结果，运行结果见最后
服务端：做一件事：接受客户端的TCP链接后，向客户端发送一个字符串，但是总在发送的地方返回值为0.求解。。。。

#include<iostream>
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<unistd.h>
#include<string.h>
#include<time.h>
using namespace std;

int main(int argc,char* argv[])
{

    int listenfd,confd;
    sockaddr_in recaddr;
    char receiveline[100]="I have received the msg\r\n";

    listenfd = socket(PF_INET,SOCK_STREAM,0);
    if(listenfd<0)
    {
        cout<<"error socket"<<endl;
        return 0 ;
    }


    bzero(&recaddr,sizeof(recaddr));

    recaddr.sin_family = PF_INET;
    recaddr.sin_addr.s_addr = INADDR_ANY;
    recaddr.sin_port = htons(7999);

    if(bind(listenfd,(sockaddr*)&recaddr,sizeof(recaddr))<0)
    {
        cout<<"bind error"<<endl;
        return 0;
    }

    if(listen(listenfd,20)<0)
    {
        cout<<"listen error"<<endl;
        return 0;
    }

    for(;;)
    {
        if(confd = accept(listenfd,(sockaddr*)NULL,NULL)<=0)
        {
            cout<<"connect error"<<endl;
            return 0;
        }
        cout<<receiveline<<endl;

        if(send(confd,receiveline,strlen(receiveline),0)<0)     
        {
**//每次都会走到这里面来，不知道为什么这个地方发送的数据为0**
            cout<<"send empty msg"<<endl;
            return 0;
        }
        if(close(confd)<0)
        {
            cout<<"faile to close socket"<<endl;
            return 0;
        }

    }
    cout<<"end of program"<<endl;
    return 0;
}

客户端：

#include<iostream>
#include<netinet/in.h>
#include<string.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>
using namespace std;
int main(int argc,char* argv[])
{
    if(argc!=2)
    {
        cout<<"wrong input"<<endl;
        return 0;
    }
    int sendfd,n;
    sockaddr_in addr;
    bzero(&addr,sizeof(addr));
    sendfd = socket(PF_INET,SOCK_STREAM,IPPROTO_TCP);
    if(sendfd<0)
    {
        cout<<"error in socket"<<endl;
        return  0;
    }

    addr.sin_family = PF_INET;
    addr.sin_port = htons(7999);
    addr.sin_addr.s_addr= inet_addr("127.0.0.1");

    cout<<"ready to connect"<<sendfd<<endl;

    if(connect(sendfd,(sockaddr*)&addr,sizeof(addr)) < 0)
    {
        cout<<"connecting fail"<<endl;
        return 0;
    }
    cout<<"ready to read:"<<sendfd<<endl;

    char receiveline[100] = {0};

    while( (n = recv(sendfd,receiveline,100,0)) > 0 )   
    {
        cout<<"n:"<<n<<endl;
        receiveline[n] = 0;

        if(fputs(receiveline,stdout)==EOF)
        {
            cout<<"error"<<endl;
            return 0;
        }
    }   

    if(n<0)
    {cout<<"error"<<endl;}

    cout<<"end of program"<<endl;   
    return 0;
}

目前程序的输出为：
服务端：
[joker@localhost serv]$ ./SocketServ
I have received the msg

send empty msg
客户端：
[joker@localhost cli]$ ./SocketCli 127.0.0.1
ready to connect3
ready to read:3
end of program
这问题搞了我两天了，求大侠们解。。。

Answer 1

大胸地，写代码要认真啊
改成 if ( ( confd = accept(listenfd, (sockaddr*)NULL, NULL ) ) <= 0)