how do I disconnect inactive clients with TIdTCPServer? - delphi

Question

I am trying to disconnect inactive clients that are connected to TIdTCPServer, whether those clients are disconnected from their Internet or for a period of inactive time.
I tried to set timeouts in the OnConnect event like the following:
procedure TservForm.TcpServerConnect(AContext: TIdContext);
begin
AContext.Connection.IOHandler.ReadTimeout := 26000;
AContext.Binding.SetSockOpt(Id_SOL_SOCKET, Id_SO_SNDTIMEO, 15000);
end;
But it seems a disconnect is not triggered after the client connection is lost.
I tried to use SetKeepAliveValues(), but it takes too much time to get an inactive client disconnected.
Is there a more helpful way to disconnect inactive clients? So if the client did not receive or send anything, for example in 30 seconds, the server will disconnect it?
on execute event
procedure TservForm.TcpServerExecute(AContext: TIdContext);
var
Connection: TConnection;
cmd: String;
Cache, OutboundCmds: TStringList;
MS: TMemoryStream;
I: integer;
S: String;
begin
Connection := AContext as TConnection;
// check for pending outbound commands...
OutboundCmds := nil;
try
Cache := Connection.OutboundCache.Lock;
try
if Cache.Count > 0 then
begin
OutboundCmds := TStringList.Create;
OutboundCmds.Assign(Cache);
Cache.Clear;
end;
finally
Connection.OutboundCache.Unlock;
end;
if OutboundCmds <> nil then
begin
for I := 0 to OutboundCmds.Count - 1 do
begin
AContext.Connection.IOHandler.Writeln(OutboundCmds.Strings[I],
IndyTextEncoding_UTF8);
MS := TMemoryStream(OutboundCmds.Objects[I]);
if MS <> nil then
begin
AContext.Connection.IOHandler.DefStringEncoding := IndyTextEncoding_UTF8;
AContext.Connection.IOHandler.LargeStream := true;
AContext.Connection.IOHandler.Write(MS, 0, true);
end;
end;
end;
finally
if OutboundCmds <> nil then
begin
for I := 0 to OutboundCmds.Count - 1 do
OutboundCmds.Objects[I].Free;
end;
OutboundCmds.Free;
end;
// check for a pending inbound command...
if AContext.Connection.IOHandler.InputBufferIsEmpty then
begin
AContext.Connection.IOHandler.CheckForDataOnSource(100);
AContext.Connection.IOHandler.CheckForDisconnect;
if AContext.Connection.IOHandler.InputBufferIsEmpty then
begin
Exit;
end;
end;
cmd := AContext.Connection.Socket.ReadLn(IndyTextEncoding_UTF8);
...............
...............

Answer 1

The client does not disconnect because the ReadLn() is not reached during idle times, so the ReadTimeout does not have effect, and if you are not sending a lot of commands then the socket buffer is not filling up so SO_SNDTIMEO does not have an effect, either.
Since you are already doing some manual timeout handling, you can expand on it to handle an idle timeout as well, eg:
type
TConnection = class(TIdServerContext)
...
public
LastSendRecv: LongWord;
...
end;
...
procedure TservForm.TcpServerConnect(AContext: TIdContext);
var
Connection: TConnection;
begin
Connection := AContext as TConnection;
AContext.Connection.IOHandler.DefStringEncoding := IndyTextEncoding_UTF8;
AContext.Connection.IOHandler.LargeStream := True;
AContext.Connection.IOHandler.ReadTimeout := 30000;
AContext.Binding.SetSockOpt(Id_SOL_SOCKET, Id_SO_SNDTIMEO, 15000);
Connection.LastSendRecv := Ticks;
end;
procedure TservForm.TcpServerExecute(AContext: TIdContext);
var
Connection: TConnection;
cmd: String;
Cache, OutboundCmds: TStringList;
MS: TMemoryStream;
I: integer;
S: String;
begin
Connection := AContext as TConnection;
// check for pending outbound commands...
OutboundCmds := nil;
try
Cache := Connection.OutboundCache.Lock;
try
if Cache.Count > 0 then
begin
OutboundCmds := TStringList.Create;
OutboundCmds.Assign(Cache);
Cache.Clear;
end;
finally
Connection.OutboundCache.Unlock;
end;
if OutboundCmds <> nil then
begin
for I := 0 to OutboundCmds.Count - 1 do
begin
AContext.Connection.IOHandler.WriteLn(OutboundCmds.Strings[I]);
MS := TMemoryStream(OutboundCmds.Objects[I]);
if MS <> nil then
AContext.Connection.IOHandler.Write(MS, 0, true);
end;
Connection.LastSendRecv := Ticks;
end;
finally
if OutboundCmds <> nil then
begin
for I := 0 to OutboundCmds.Count - 1 do
OutboundCmds.Objects[I].Free;
end;
OutboundCmds.Free;
end;
// check for a pending inbound command...
if AContext.Connection.IOHandler.InputBufferIsEmpty then
begin
AContext.Connection.IOHandler.CheckForDataOnSource(100);
AContext.Connection.IOHandler.CheckForDisconnect;
if AContext.Connection.IOHandler.InputBufferIsEmpty then
begin
if GetTickDiff(Connection.LastSendRecv, Ticks) >= 30000 then
AContext.Connection.Disconnect;
Exit;
end;
end;
cmd := AContext.Connection.Socket.ReadLn;
Connection.LastSendRecv := Ticks;
...
end;