GetAcceptExSockaddrs returns garbage! Does anyone know why?

Question

[I've followed the suggestion to use Winsock.pas, but it still writes garbage -- although the sin_family field has changed to a new garbage value.]

Hello, I'm trying to write a quick/dirty echoserver in Delphi, but I notice that GetAcceptExSockaddrs seems to be writing to only the first 4 bytes of the structure I pass it.

program TCPEcho;
{$APPTYPE CONSOLE}

uses Windows, SysUtils, Winsock;
type INT = SmallInt;

const
    BufDataSize = 8192;
    BufAddrSize = SizeOf (TSockAddrIn) + 16;
var
    WSAData : TWSAData;
    ListenSock, AcceptSock : TSocket;
    Addr, LocalAddr, RemoteAddr : TSockAddrIn;
    LocalAddrSize, RemoteAddrSize : Integer;
    Ov : OVERLAPPED;
    Buf : array[1..BufDataSize + BufAddrSize * 2] of Byte;
    BytesReceived : DWORD;
begin
    FillChar (WSAData, SizeOf (WSAData), 0);
    WSAStartup (2, WSAData);

    ListenSock := ValidSocketCheck ('Socket', Socket (AF_INET, SOCK_STREAM, IPPROTO_TCP));

    FillChar (Addr, SizeOf (Addr), 0);
    Addr.sin_family := AF_INET;
    Addr.sin_port := HToNS (1066);
    Addr.sin_addr.s_addr := HToNL (INADDR_ANY);
    SocketCheck ('bind', bind (ListenSock, Addr, SizeOf (Addr)));

    SocketCheck ('Listen', Listen (ListenSock, 3));


    FillChar (Ov, SizeOf (Ov), 0);
    Ov.hEvent := HandleCheck ('CreateEvent', CreateEvent (nil, False, False, nil));

    AcceptSock := ValidSocketCheck ('Socket', Socket (AF_INET, SOCK_STREAM, IPPROTO_TCP));
    if AcceptEx (ListenSock, AcceptSock, @Buf, BufDataSize, BufAddrSize, BufAddrSize, BytesReceived, @Ov) then
        WinCheck ('SetEvent', SetEvent (Ov.hEvent))
    else
        if GetLastError <> ERROR_IO_PENDING then
            WinCheck ('AcceptEx', GetLastError);

    if WaitForMultipleObjects (1, @Ov.hEvent, False, INFINITE) <> WAIT_OBJECT_0 then
        raise Exception.Create ('WFMO');


    GetAcceptExSockaddrs (@Buf, BufDataSize, BufAddrSize, BufAddrSize, LocalAddr, LocalAddrSize, RemoteAddr, RemoteAddrSize);
    WriteLn (RemoteAddr.sin_family);
end.

So if I run this, connect to it with Telnet (on same computer, connecting to localhost) and then type a key, WaitForMultipleObjects will unblock and GetAcceptExSockaddrs will run. But the result is garbage!

RemoteAddr.sin_family = 51618
RemoteAddr.sin_port = 64 

and the rest is zeroes.

What gives? Thanks in advance!

Answer 1

What Delphi version are you using? In any case where is no need to use your own type definitions for GetAcceptExSockaddrs and its arguments, use the definitions from WinSock.pas unit; they differ from yours definitions at least for unicode Delphi versions.

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Updated

Looks like the definition of GetAcceptExSockaddrs is wrong. I remember old Delphi versions contained a bug here. The correct prototype (taken from Delphi 2009 WinSock.pas) is

procedure GetAcceptExSockaddrs(lpOutputBuffer: Pointer;
  dwReceiveDataLength, dwLocalAddressLength, dwRemoteAddressLength: DWORD;
  var LocalSockaddr: PSockAddr; var LocalSockaddrLength: Integer;
  var RemoteSockaddr: PSockAddr; var RemoteSockaddrLength: Integer); stdcall;

Note that LocalSockaddr and RemoteSockaddr are not pointers to structures but pointers to pointers to structures.