Socket cannot receive data? Client is written using Boost.asyio library. Server is written in python

Question

client code

#include <cstdlib>
#include <iostream>
#include <memory>
#include <utility>
#include <boost/asio.hpp>
#include <string>
#include <boost/array.hpp>

using namespace std;
using namespace boost::asio;

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

    io_service service;
    ip::tcp::endpoint ep(ip::address::from_string("127.0.0.1"), 2001);

    ip::tcp::socket sock(service);
    sock.connect(ep);

    boost::asio::streambuf sb;
    boost::system::error_code ec;
    size_t len;
    while (true)
    {
        //write data
        sock.write_some(buffer("ok", 2));
        //read data
        read(sock, sb, transfer_all(),ec);
        //handle error
        if (ec && ec != error::eof) {
            std::cout << "receive failed: " << ec.message() << std::endl;
        }
        else {
            const char* data = buffer_cast<const char*>(sb.data());
            std::cout << data << std::endl;
        }
    }
    return 0;
}

server code

import socket
import threading

s = socket.socket()
s.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1)
s.bind(("127.0.0.1",2001))

s.listen(5)
cons = []

print "begin....."
while True:
    con,addr = s.accept()
    #cons.append(con)
    print con
    while True:
        data = con.recv(1024)
        if not data:
            con.close()
            break;
        print data
        con.send("123")
s.close()

Client can send "ok" to the server, but it cannot receive "123" from the server.

If I use a client written in python, the server and client can communicate well.

Could someone tell the reason about this mistake?

Answer 1

Use the tcp::socket::read_some method. This method blocks until something gets received to the socket and then reads the data (while the read(...) function reads the whole file/socket until EOF, which only occurs if the connection drops)

You can read up the usage here.

Example:

std::string recbuf;
while (true)
{
    //write data
    sock.write_some(buffer("ok", 2));
    //read data
    sock.read_some(buffer(recbuf, 1024), ec);
    //handle error
    if (ec && ec != error::eof) {
        std::cout << "receive failed: " << ec.message() << std::endl;
    }
    else {
        std::cout << recbuf << std::endl;
    }
}

Answer 2

I have found similar question boost::asio::ip::tcp::socket doesn't read anything .

Using read_until can solve this question.