服务器无法打印从客户端获取的数据

Question

My client code sends some data to the server when it connects to it and I want that data to be printed by the server on the screen.But it is giving quite a strange out not what I am sending. Here is my server and client code:

#include <iostream>
#include "server.h"

Server::Server()
{

}

void Server::CreateSocket()
{
server_sockfd = socket(AF_INET, SOCK_STREAM,0);
if(server_sockfd < 0)
{
    std::cout <<  "Error creating socket\n"<<std::endl;
    exit(1);
}
std::cout << "Server socket created\n" <<std::endl;
}

void Server::NameSocket()
{
server_address.sin_family = AF_INET;
server_address.sin_addr.s_addr = inet_addr("127.0.0.1");
server_address.sin_port = htons(1500);

if((bind(server_sockfd, (struct sockaddr *)& server_address, sizeof(server_address)))<0)
{
    std::cout<<"Error binding socket\n"<<std::endl;
    exit(1);
}

std::cout <<"Server naming done \n"<<std::endl;
}

void Server::CreateQueue()
{
listen(server_sockfd, 1);
std::cout <<"Server Create queue done \n"<<std::endl;
}

void Server::AcceptConnection()
{
size = sizeof(server_address);
client_sockfd = accept(server_sockfd,(struct sockaddr*)&server_address, &size);
if(client_sockfd < 0)
{
    std::cout << "Can't accept connection\n"<<std::endl;
    exit(1);
}

std::cout <<"Server accept connection done"<<std::endl;
}

void Server::ReadWriteSocket()
{
while(true)
{
    char *buffer;
    // Server reading data coming from the client
    read(client_sockfd, &buffer, sizeof(buffer));
    //std::cout <<buffer<<std::endl;( Problem Comes here )

    // Server writing data to the client
    //write(client_sockfd, & buffer1,sizeof(buffer1));
    //std::cout << buffer1<<std::endl;
    close(client_sockfd);
}
}

Client Code:

   #include <iostream>
   #include "client.h"


   Client::Client()
  {
    this->_Flag = false;
  }


// Create a socket for client
void Client::CreateSocket()
{
   if((sockfd = socket(AF_INET, SOCK_STREAM,0)) < 0)
{
    perror("Socket not created");
    exit(1);
}

std::cout << "Client Socket created \n"<<std::endl;
}
//Name socket as agreed with a server
void Client::NameSocket()
{
address.sin_family = AF_INET;
address.sin_addr.s_addr = inet_addr("127.0.0.1");
address.sin_port = htons(1500);
std::cout<<"Client name socket done \n"<<std::endl;
}

void Client::ConnectSocket()
{
 // Now connect out socket to server socket
result = connect(sockfd, (struct sockaddr*)&address, sizeof(address));
if(result == -1)
{
    std::cout << "Can't establish connection\n"<<std::endl;
    exit(1);
}

 std::cout << "Connect to server socket done \n"<<std::endl;
}
// We can now read and write via sockfd
void Client::ReadWriteSocket()
{
  char *buffer= "Hello from the client";
_Flag = true;
while(_Flag)
{
write(sockfd, &buffer, sizeof(buffer));
std::cout <<buffer<<std::endl;
//std::cout<<buffer1<<std::endl;
//read(sockfd,& buffer, sizeof(buffer));
close(sockfd);
}

}

input : Hello from the client

output should be same but instead I am getting: U D$ U D$ U D$ U D$ U D$ U D$ U D$ U D$ U D$ U D$ U D$ U D$ U D$ U D$

Answer 1

In the method Server::ReadWriteSocket()

write(sockfd, &buffer, sizeof(buffer));
std::cout <<buffer<<std::endl;

you print the buffer which has no ending zero to mark string end (another problem is that buffer does not have memory reserved, so the server could crash). Thus, it prints any random bytes found in buffer after the content. Also, check the number of bytes returned by read and use it to determine end of the buffer . The same holds for Client::ReadWriteSocket() .