I am currently writing two projects that have to communicate with each other over TCP, with the client having to be implemented using System::Net::Sockets, and the server using c++ winsock. For a long time, I have been using this lovely function to receive text in winsock, where the client sends the message length first and then the message. I don't want to have to change anything on the server side with this function, but with the .NET I will do anything. This is my attempt.
bool WinSockObject::receiveText(std::string &out)
{
//Create a temporary buffer to work with
char buf[4096];
//Stores textLength of incoming data
long textLength = 0;
//Receive the textLength that was sent first
_result = ::recv(
_socket, //socket we are receiving on
reinterpret_cast< char *>(&textLength), //the length of the incoming text
sizeof(textLength), //number of bytes
0 //no additional flags necessary
);
//Make sure we got the text length
if (_result == SOCKET_ERROR)
{
set_error("Unable to receive text length.");
return false;
}
//Convert the textLength back to host bytes
textLength = ::ntohl(textLength);
//Receive the actual message
_result = ::recv(
_socket, //socket we are receiving on
buf, //the input buffer
textLength, //text length
0 //no additional flags are necessary
);
//Make sure we got the actual message
if (_result == SOCKET_ERROR)
{
set_error("Unable to receive text.");
return false;
}
//Manually terminate the buffer
buf[textLength] = '\0';
//Copy the buffer to the output string
out.append(buf);
return true;
}
But I am stuck sending the length first then the message
Socket^ s = gcnew Socket(
AddressFamily::InterNetwork,
SocketType::Stream,
ProtocolType::Tcp
);
s->Connect(se开发者_JAVA百科rver, port); //message to send
String^ howdy = "howdy";
int strLength = howdy->Length; //length of message
String^ length = strLength.ToString(); //convert it to String
//get the bytes
array<Byte>^msgLength = Encoding::ASCII->GetBytes(length);
//send the message length
int bytes = s->Send(msgLength);
//send the actual message
array<Byte>^msg = Encoding::ASCII->GetBytes(howdy);
bytes = s->Send(msg);
There are two problems that I see after a brief reading:
- You're sending the string length as a string, but the server is reading it as binary.
- The server is assuming that
recv
will always read the number of bytes requested. This is wrong;recv
may return 0 (if the other side has closed the connection gracefully), any value in the range [1, len] (if some data was received successfully), or SOCKET_ERROR (if there was an error).
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