C++/CLI Timer freezes applications - winforms

Question

I am using a timer in a c++ windows form app. To handle receiving messages sent from a server using WinSock2. The current code for my timer is,
private: System::Void tmrMessages_Tick(System::Object^ sender, System::EventArgs^ e) {
int ID;
char* cID = new char[64];
char* message = new char[256];
ZeroMemory(cID, 64);
ZeroMemory(message, 256);
if(recv(sConnect, message, 256, NULL) != SOCKET_ERROR && recv(sConnect, cID, 64, NULL) != SOCKET_ERROR)
{
ID = atoi(cID);
if (ID == 1)
{
lbxMessages->Items->Add("hello");
}
}
}
I didn't have it add the variables to the listbox because I wanted to test and make sure it worked first. It DOES work but, it makes the app so slow that it doesn't allow any user input at all. It does show the listbox being updated but, like I said doesn't allow me to move the window, click textboxes or anything. If you have any idea why this is happening please let me know.
thanks.

Answer 1

If those are blocking reads, they'll freeze the UI thread until you get data.
What you should do is set non-blocking mode and read until you fill your buffer, which may take multiple recv calls, the process it.
I really like WSAAsyncSelect for this... it automatically puts the socket into non-blocking mode and sends your window a message whenever data is available. You can easily handle that message by overriding WndProc.
It should be pretty straightforward:
#include <winsock2.h>
#include <windows.h>
const unsigned WM_SOCKETREADY = WM_USER + 100;
...
when you open the socket (assuming that's a member function of the form), call
WSAAsyncSelect(sConnect, HWND(Handle.ToPointer()), WM_SOCKETREADY, FD_READ);
and then WndProc (which you should override) will have the message delivered to it
virtual void WndProc( Message% m ) override
{
switch (m.Msg) {
case WM_SOCKETREADY:
ReadSocketHandler();
return;
default:
Form::WndProc(m);
return;
}
}