n的值是9，sockfd = 3，当它调用read函数时，它不是从read函数中出来的。在打印读取开始行后，它仅在此处停止：

while(1)
{
        if (n < 0)  
            {
                printf("ERROR writing to socket");              
            }   
        else if(n == 0)
            {
                printf("Nothing");

            }
            printf(" read start n=%d\n ,sockfd = %d\n",n,sockfd);
            n = read(sockfd,buffer,1024);

        if (n < 0)
            {   error("ERROR reading from socket");
            }
            printf("Reply= %s",buffer);
            write_buf_to_file("/root/abc_regr/receive.txt",buffer);  
}
return;