Synapse TTCPBlockSocket on network load balancing and proxy protocol enabled

Question

We have an application server, a TCP protocol type and stream socket type, that is behind an NGINX load balancer but planned to be migrated to AWS with either NLB or ALB. Based on the info I got from the answers of the related questions here in StackOverflow, ALB is only for HTTP/HTTPS so it might not be a good option for our case. Anyway, based on AWS's documentation here, https://docs.aws.amazon.com/elasticloadbalancing/latest/network/load-balancer-target-groups.html#client-ip-preservation, “Before enabling proxy protocol on a target group, the application server must expect and can parse the proxy protocol v2 header, otherwise, it might fail". Could it be the reason why clients cannot access the application server when Proxy Protocol V1 or V2 is enabled at proxy server or load balancer?

The issue is our client apps can connect to the application server when proxy protocol is disabled but not when enabled.

Below are the code snippets. The class variable FSocket is of TTCPBlockSocket type and CanRead is TBlockSocket method under blcksock unit of Synapse library. I suspect that "if FSocket.CanRead(1000)" always returns false, because it doesn't stop to the next line when I set debug break point. I was thinking of parsing the proxy protocol header to know if information related to it is available. When it is available the application will just proceed to create the client session. Not sure if that is a good idea. But even if it is, I do not know how to do it. Does anybody familiar with Synapse and has worked with proxy protocol before? Any idea or code samples on parsing proxy protocol header for me to start with? Thanks in advance.

procedure TSynapseMidasDaemon.Execute;
var
  lClientHandle: TSocket;
  lSession: TSynapseMidasSession;
begin
  FSocket.CreateSocket;
  FSocket.Bind(FIPAddress, IntToStr(FPort));
  FSocket.setLinger(True, 1000);

  FSocket.Listen;
  while not Terminated do
  begin
    if FSocket.CanRead(1000) then
    begin
      lClientHandle := FSocket.Accept;
      if FSocket.LastError = 0 then
      begin
        // we have a winner
        try
          // create a client session
          lSession := TSynapseMidasSession.Create(Self, lClientHandle, FLogSystem, FSettings);
          lSession.Resume;
        except
          on e: Exception do
          begin
            LogEventFmt(evlError, 'Daemon Socket Failure [%s]', [e.Message]);
            InterlockedDecrement(FStatistics.Accepted);
            InterlockedIncrement(FStatistics.Rejected);
          end;
        end;
      end; //else we had a socket failure.  Moving on.
    end;
    Sleep(0);// play nice with others.
  end;
end;

function TBlockSocket.CanRead(Timeout: Integer): Boolean;
var
  ti, tr: Integer;
  n: integer;
begin
  if (FHeartbeatRate <> 0) and (Timeout <> -1) then
  begin
    ti := Timeout div FHeartbeatRate;
    tr := Timeout mod FHeartbeatRate;
  end
  else
  begin
    ti := 0;
    tr := Timeout;
  end;
  Result := InternalCanRead(tr);
  if not Result then
    for n := 0 to ti do
    begin
      DoHeartbeat;
      if FStopFlag then
      begin
        Result := False;
        FStopFlag := False;
        Break;
      end;
      Result := InternalCanRead(FHeartbeatRate);
      if Result then
        break;
    end;
  ExceptCheck;
  if Result then
    DoStatus(HR_CanRead, '');
end;