TCP RECV buffer length

[Steven Pringels 3]

Hi everybody,

what is the maximum buffer length in the TCP RECV statement. Is
this 1024 bytes or can it be anything higher (32 KB ?), although
I tried that but it didn't work. Can you augment the buffersize ?

Steve.

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[Lance Edmonds]

I'm not aware that there is an arbitary limit imposed by PowerBASIC, however, it is usually better to read in smaller chunks and assemble it all together while checking for errors. Something like this:

CASE %FD_READ
  Buffer$ = ""
  Chunk$ = ""
  ERRCLEAR
  DO
    TCP RECV #hTcp, 1024, Chunk$
    Buffer$ = Buffer$ + Chunk$
  LOOP WHILE ISTRUE LEN(Buffer$) AND ISFALSE EOF(hTcp) AND ISFALSE ERR

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Dominic Mitchell]

ISTRUE LEN(Buffer$) AND ISFALSE EOF(hTcp) AND ISFALSE ERR

Lance, shouldn't the statement shown above be

(ISTRUE LEN(Buffer$)) AND (ISFALSE EOF(hTcp)) AND ISFALSE ERR

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Dominic Mitchell

[Lance Edmonds]

Why? It is using Short-Circuit evaluation and how it works is instantly clear without adding parentheses.

Actually there was an error in that statement... it should have read:

LOOP WHILE ISTRUE LEN(Chunk$) AND ISFALSE EOF(hTcp) AND ISFALSE ERR

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Semen Matusovski]

steven --
1024 is a figure from the sky.
below is a fragment, which i wrote before poffs appearence.
play with kbuffer.
you can increase it, lets say to 32k, but (it seems to me) web-site sends chunks 8k maximum.
99,99% sure that web-server defines maximum size of chunks.
of course, own buffer should be enough large to avoid additional restrictions (i think 8-16k, but better to test certain web sites).

[CODE]
#compile exe
#register none
#dim all
#include "win32api.inc"

$forum = "4"
%idx1 = 1100
%idx2 = 1110
function pbmain
dim buffer as string, kbuffer as long, i as long, j as long
dim idx as long, pgnm as string, pref as string
for idx = %idx1 to %idx2
pref = "
do
tcp open port 80 at "www.powerbasic.com" as #1 timeout 5000
pgnm$ = format$(idx, "000000") + pref + ".html"
cls: print pgnm$
tcp print #1, "get <a href="http://ru

[Steven Pringels 3]

Hi,

Yes, I guess everybody's right concerning the 1024, i need to
check for the length of the buffer. Now I seem to have another
problem. I send a structure. The structure contains the
member length. Length is defined as a Long. When I put the
value 10 in there which is a Line Feed char, and send that
the receiving part gets confused. It thinks it is a LF. How to
solve this one ?

I came up with a check of the length. if the length is less than
26 (special chars) I make the value negative and then on the client
side I use the ABS to obtain the length. It works but is this the
way to do it or are there other alternatives?


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[Lance Edmonds]

You are on the right track - you need to work out your own "data protocol" so that you can transfer binary data back and forward without regard to how TCP actually gets the data there.

You may also want to add some form of checksum into the data to make sure the packets contain reliable data, and that you can pick out a "structure" from the data with reliability.

PS: you should be using TCP RECV rather than TCP LINE if you are passing binary data.

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Dominic Mitchell]

istrue and isfalse are unary operators, and as such, potentially affect every operand
to the right (subject to precedence rules). you appear to be expecting them to act as
functions, affecting only the operands within parentheses. an incorrect interpretation.

that is a quote from bob. see the following http://l]http://l

the loud description of the debugger was bad form on my part. sorry about that.

ps
disregard my previous posts. my head finally cleared. i think i got up too early.

[this message has been edited by dominic mitchell (edited june 18, 2001).]

[Semen Matusovski]

My "updater", which works on hundreds PCes, downloads binary files from HTTP (using TCP RECV) without any problems.
Control - yes, it's necessary. I attach even two independent CRC32 to all files.

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E-MAIL: [email protected]

[Don Dickinson]

I have run into a limit of 64 k, but I can't remember if that was sending or receiving.
--Don

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dickinson.basicguru.com