Win32 C++ using HWND in separate file/thread to start timer - winapi

Question

Background:
Application Type: Win32 Application
Language: C++ (with C functions as well)
Problem: Want to use main Window Handle in another file.
Update 1: Using a TCP server in another thread. This server receives information from a client and then needs to start a timer in the program.
Project Layout:
Main File: main.cpp/main.h which has WinMain, WndProc, etc.
Other Generated Files: Resource.h, main.rc, stdafx.h etc generated by Visual Studio
Self Made Files: functions.cpp/functions.h & calculation.cpp/calculation.h
Update 1: Server thread is in the main.cpp file and the call to start the timer is made on the server thread. I also updated some of the code to more accurately reflect what I have.
Info:
Can I call SetTimer(hwnd, TIMER_INT, TIMER_INTERVAL, NULL) in the calculation.cpp file in some way and make the TIMER_INT timer trigger in the WndProc for WM_TIMER?
So for example (of course foo is defined in calculation.h, etc. for other functions).
//calculation.cpp
void foo(HWND hwnd)
{
SetTimer(hwnd, TIMER_INT, TIMER_INTERVAL, NULL);
}
//functions.cpp
void ThreadStart()
{
/* This code initializes a working server that is visible to main.cpp */
/* The Server socket and Accept socket are extern for main.cpp */
}
//main.cpp
HWND hwnd;
int WinMain(...)
{
//... Set hwnd here
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, ...)
{
static PARAMS params; //Thread params
switch(message)
{
case WM_CREATE:
//This initializes a blocking Server (which works)
params.hwnd = hWnd;
params.bContinue = TRUE;
_beginthread(ThreadServer, 0, &params);
break;
case WM_TIMER:
case TIMER_INT:
MessageBox(NULL, L"Timer was triggered from foo", L"FOO", NULL);
//continuous messageboxes will appear based on TIMER_INTERVAL if it works...
break;
break;
}
}
void ThreadServer(PVOID pvoid)
{
ThreadStart(); //calls accept() until client connects
while(1)
{
memset(&RecvBuffer[0], 0, 512 * sizeof(RecvBuffer[0])); //Clear recv
TCPServer.iRecv = recv(AcceptSocket, RecvBuffer, iRecvBuffer, 0);
if(strlen(RecvBuffer) > 1){
memset(&SendBuffer[0], 0, 512 * sizeof(SendBuffer[0]));
//Clears SendBuffer
std::string retString = "";
retString = process(RecvBuffer); //processes RecvBuffer
if(condition == true){
foo(hwnd);
}
if(strlen(retString.c_str()) > 0){
TCPServer.iSend = send(AcceptSocket, retString.c_str(), strlen(retString.c_str()), 0);
}else{
retString = "";
TCPServer.iSend = send(AcceptSocket, retString.c_str(), strlen(retString.c_str()), 0);
}
if(TCPServer.iSend == SOCKET_ERROR){
break;
}
}
//Determine if socket fails and breaks if failure occurs
//*
memset(&SendBuffer[0], 0, 512 * sizeof(SendBuffer[0]));
TCPServer.iSend = send(AcceptSocket, SendBuffer, iSendBuffer, 0);
if(TCPServer.iSend == SOCKET_ERROR){
break;
}//*/
Sleep(1);
}
}
The issue is trying to pass a reference to hwnd to calculation.cpp from the server thread. I can pass hwnd to the function foo(HWND), but the timer does not set. Is there a way to set a timer in a separate thread or is this not possible? Is there any other workaround to this with using winsock and a server?

Answer 1

As the document state that you can't create a timer for a window from a different thread. For you the different thread is the server thread.
Maybe you can post WM_TIMER message (PostMessage) to the main thread from the server thread when the timer timeout.
Or you need Synchronization Objects for threads synchronicity.