TCP client in Boost asio - c++

Question

Im building a TCP client using Boost::asio Libs. My program has a write() thread that sends a command to the server
write(*_socket,boost::asio::buffer("sspi l1\n\n",sizeof("sspi l1\n\n")));
Then a read thread is started that reads from the buffer all the time, as there can be messages broadcasted from the server due to any other client
void TCP_IP_Connection::readTCP()
{
size_t l=0;
this->len=0;
boost::system::error_code error;
try
{//loop reading all values from router
while(1)
{
//wait for reply??
l=_socket->read_some(boost::asio::buffer(this->reply,sizeof(this->reply)),error);
if(error)
throw boost::system::system_error(error);
if(l>0)
{
this->dataProcess(l);
}
else
boost::this_thread::sleep(boost::posix_time::milliseconds(5000));
_io.run();
if(error==boost::asio::error::eof) //connection closed by router
std::cout<<"connection closed by router";
_io.reset();
}
}
catch (std::exception& e)
{
std::cerr << e.what() << std::endl;
}
}
This thread runs al time in a while(1) loop and is supposed to sleep when the received data length is less than zero. It reads all the data and calls the data parser function. After that the write thread is used to send another command, with read thread running. But instead of the required response the server sends back
? ""
ERROR: Unknown command
I tried using the wireshark. I can see the command being send properly. What can be mistake I'm doing here?

Answer 1

sizeof("sspi l1\n\n") returns 10, but I can only count 9 characters in that string.
Try this instead:
const std::string cmd("sspi l1\n\n");
write(*_socket,boost::asio::buffer(cmd, cmd.length()));
Or when you have it as a string it is enough to do
const std::string cmd("sspi l1\n\n");
write(*_socket,boost::asio::buffer(cmd));
The second argument specifies a maximum length of the string to use. But since it is a constant string, the second argument is not strictly necessary.