I used this snipped of code to enable tcp keepalives under windows (xp, 32
bits):
(FChannel is a TTCPBlockSocket):
FChannel.Connect(FAddress,Fort);
if FChannel.LastError=0 then
begin
DoLog(LogInfo,'connected');
FConnected:=true;
keepalive.onoff:=1;
keepalive.keepalivetime:=10000;
keepalive.keepaliveinterval:=1000;
if
wsaioctl(FChannel.Socket,
SIO_KEEPALIVE_VALS,
@Keepalive,
sizeof(Keepalive),
nil, //lpvOutBuffer
0, //cbOutBuffer
@dummy, //lpcbBytesReturned
nil, //lpvOverlapped
nil //lpCompletionRoutine
) = 0 then
DoLog(LogInfo,'set a keepalive of 10 seconds');
This code works (though the keepalive is sent after 1 second of inactivity and
not 10),
but I found a strange problem: when I closed the program, windows kept the
socket
open and kept sending keepalives (I saw it with wireshark, sysinternals'
tcpview showed
the socket as owned by a non existent process).
This doesn't happen always (I cannot reproduce the problem at will) but it
happens.
The problem is that the peer only accepts one connection, so I cannot reconnect
when I start the program again if windows is keeping the socket open behind my
back.
I know that this isn't a synapse problem, but here is where the experts are
;-), so,
is this normal?
If I, say, disconnect the cable and close the program, I find it normal for
windows to
keep the socket around so that it can tear down the connection when the cable
is reconnected,
but I think it's strange that it keeps sending keepalives.
Bye
--
Luca
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