Problem with unresolved external symbol of a variable in a class with _beginthread

Question

I'm not sure why a static declared variable is not being recognized in my C++ class. I am using _beginthreadex(), so from what I found, it seems I need the class function containing _beginthreadex() to be declared as static.

Here is a working example, compiled with Visual Studio 2019.

The main program main.cpp simply initializes the class:

#include "CWinSock.h"
CWinSock *clsCWinSock;
INT main(INT argc, char* argv[])
{
    clsCWinSock = new CWinSock();
    while (1)
        ;    
    return 0;
}

Here is the simple class header CWinSock.h:

#pragma once
#include <Windows.h>
class CWinSock
{
    public:
        CWinSock();
        ~CWinSock();
        void CreateServer();
        static UINT dwServerPort;
    private:
        static unsigned WINAPI ListenAndAccept(void*);
};

And here is the class .cpp file:

#include <windows.h>
#include <process.h>    /* _beginthread, _endthread */
#include "CWinSock.h"

UINT CWinSock::dwServerPort;
CWinSock::CWinSock() {dwServerPort = 61801;}
CWinSock::~CWinSock() {}

static unsigned WINAPI ListenAndAccept(void *)
{
    UINT dwPort = CWinSock::dwServerPort;
    return 0;
}

void CWinSock::CreateServer()
{
    // Call the main example routine.
    UINT threadID = 0;
    HANDLE hThread = (HANDLE)_beginthreadex(NULL, 0, &ListenAndAccept, NULL, 0, &threadID);    
    WaitForSingleObject(hThread, INFINITE);
    CloseHandle(hThread);
}

This is the basics, yet I get the error: LNK2001, unresolved external symbol "public: static unsigned int CWinSock::dwServerPort" (?dwServerPort@CWinSock@@2IA). Putting UINT CWinSock::dwServerPort; in the .cpp file solves that error.

BUT, it ALSO errors on the function ListenAndAccept. Even if I declare it in the .cpp file as suggested, it still gives an error.

It doesn't give the error if I take off the static, but from what I understand (which might be incorrect), _beginthreadex() won't work without its function being static? Or I'm doing something really wrong?

Any help in calling _beginthreadex() from a class and the reason for static is appreciated also!