#include <lm.h>을 인클루드 하시고요 ...

#define MESGLEN 50
PSERVER_INFO_503 GetServerInfo(void);       // gets & displays this systems
					    // name

불러올 함수 부분에서 아래거 선언하시구요.

NET_API_STATUS     nasRc;               // return code from NetXxxx()
PSERVER_INFO_503   si503;               // Server info structure
LPWSTR             awcFromName;         // default machine name for NetMsgBufrSend()

si503 = GetServerInfo();
sprintf(_T("You are logged into domain: %s.\n"), si503->sv503_domain);

하시면 넘어올거예요

/* **************************************************************************
 * PROCEDURE: PSERVER_INFO_503 GetServerInfo(void)
 * PURPOSE:   Get the name of this server
 * CALL:      GetServerInfo()
 * RETURNS:   SERVER_INFO_503*
 * MODIFY:    Nothing
 * *********************************************************************** */
PSERVER_INFO_503 GetServerInfo(void)
{
    NET_API_STATUS     nasRc;               // return code from NetXxxx()
    LPBYTE             buff;

    nasRc = NetServerGetInfo(NULL,503,&buff);
    if(nasRc != NERR_Success)
    {
        switch(nasRc)
        {
            case ERROR_ACCESS_DENIED:     // The user does not have access to
				     // the requested information.
                               break;
            case ERROR_INVALID_LEVEL:     // The value specified for the Level parameter is invalid.
            case ERROR_INVALID_PARAMETER: // The specified parameter is invalid.
                               break;
            case ERROR_NOT_ENOUGH_MEMORY: // Insufficient memory is available.
                               break;
        }
        exit(2);
    }
    return((PSERVER_INFO_503) buff);
}

이게 제가 알아낸 전부 입니다. 도움이 되셨으면 하네요 ...