Collecting telnet server responses using lnet.
lazarus / 38-Networking and Web Programming

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cov · 2011-10-18 14:08

I am trying to telnet to connect to a TiVo DVB-T device.

When I send the device a "GET" request, the device responds with
several packets.

However, lnet will only get the first one.

Is there some way I can get lnet to wait for all packets to be
received?

I am simply sending the "GET" command

Code: [Select]Telnet.SendMessage('GET /tvnb?sessionid='+sessID+msg+'
HTTP/1.1' + #13#10 + #13#10);
And then I'm getting the response with

Code: [Select]procedure TFormMain.TelnetReceive(aSocket: TLSocket);
var s: string;
begin
  if Telnet.GetMessage(s) > 0 then
    begin
      MemoText.Append(s);     
    end;
end;

Normally all the header information is carried in the first packet and
the data is carried in subsequent packets, but I am only able to read
the first packet, although Wireshark tells me that the data packets
are being sent too.

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cov · 2011-10-20 15:37

Hmmm.

Okay, to clarify, I send this to the device:
QuoteGET
/tvnb?sessionid=0000001400c2002900&op=channellist&withrating=1
HTTP/1.1
This is actually Frame 73 of the exchange.

The device then sends back Frame 74 which is 66 bytes, followed by
Frame 75 which contains 85 bytes of data (which I can access using
Telnet.GetMessage(s):
QuoteHTTP/1.1 200 OK
Content-Type: text/plain
Content-Length: 892
X-1seg-Result: 14
Frame 76 (66 bytes) is then sent to the device, followed by Frame 77,
also 66 bytes.

The device then responds with Frame 78 Frame 79, Frame 80, Frame 81,
Frame 82 and Frame 83 (each containing 74 bytes), before it finally
sends Frame 84 which containst the data I'm interested in, namely 892
bytes of data:
Quote1_1_cbms://thomson.net/service/105|00|3|1|||0|1|en|Sony Max
1_1_cbms://thomson.net/service/111|00|3|1|||0|1|en|E! Entertainment
Mobile
1_1_cbms://thomson.net/service/108|00|3|1|||16|1|en|Africa Magic
1_1_cbms://thomson.net/service/109|00|3|1|||0|1|en|Channel O
1_1_cbms://thomson.net/service/107|00|3|1|||0|1|en|TRACE Urban
1_1_cbms://thomson.net/service/104|00|3|1|||0|1|en|SuperSport Blitz
1_1_cbms://thomson.net/service/101|00|3|1|||0|1|en|SuperSport 1
1_1_cbms://thomson.net/service/103|00|3|1|||0|1|en|SuperSport 2
1_1_cbms://thomson.net/service/102|00|3|1|||0|1|en|SuperSport 3
1_1_cbms://thomson.net/service/113|00|3|1|||0|1|en|SuperSport 4
1_1_cbms://thomson.net/service/110|00|3|1|||0|1|en|eNews
1_1_cbms://thomson.net/service/112|00|3|1|||0|1|en|CNN
1_1_cbms://thomson.net/service/106|00|3|1|||0|1|en|Cartoon Network
1_1_cbms://thomson.net/service/115|00|3|1|||18|1|en|M-Net Series

I want to know how I can access this data. Telnet.GetMessage(s) does
not give it to me.

I though that it may be an issue with the string, 's' containing a
null value which would truncate it, but the actual data doesn't
contain any such null character. If I can access Frame 75 using
GetMessage, why can I not access Frame 84?

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Almindor · 2011-11-03 14:03

This may be a FPC issue with strings, try using .GET instead of
.GETMESSAGE to see if it differs.

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cov · 2011-11-28 08:57

Hi Almindor,

Thanks for the response.

Is there anywhere I can get the syntax for implementing the GET
function?

Many thanks

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BigChimp · 2011-11-28 10:39

FYI, you can also have a look at this small telnet client implemented
using synapse: http://wiki.lazarus.freepascal.org/Synapse#Requirements