[Gambas-user] gb3 RC1: using structures to replace the loss of Mk$ functions

[Benoît Minisini]

> On 04/05/2011 01:39 AM, Kevin Fishburne wrote:
> > Alright, I've transformed all the networking code to the suggested
> > solution, and it's so close to working I can smell it. While there is
> > more code now, I like it better as it's easier to read (important!).
> > 
> > Some code:
> >     Dim id As Byte
> >     Dim type As Byte
> >     Dim data As String
> >     
> >     id = Read #udp As Byte
> >     type = Read #udp As Byte
> >     If Eof(udp) = False Then data = Read #udp, Lof(udp) - 2
> > 
> > Using "Lof(udp) - 2" as the length seems to remove bytes from the end
> > rather than the beginning. I get an unwanted byte at the beginning as
> > well.
> > 
> > Maybe this is a late April Fools joke about endianness? Other than that,
> > the whole app is ready to put pixels on the screen again
> 
> After checking my code for bugs (none found, knock on wood) and doing
> some experimentation, it looks like sending certain data types using the
> new method works fine, but other data has an extra byte added in front
> of or in-between variables. Any info about what's really happening is
> appreciated.
> 
> Again what I'm trying to do is send an ID (Byte), type (Byte), and a
> sequence of arbitrary variables via UDP. When they're received, the ID
> and type are read normally as Bytes into variables and the rest of the
> data is read into a string and stored in an array for later processing.
> The arbitrary variables stored as a string (everything after ID and
> type) are later interpreted via the *@() functions and assigned to
> variables. To do this I just created a different UDP_Write procedure for
> each transaction type so the packets/transactions are properly
> assembled. I've attached some code excerpts if anyone desires greater
> specificity.
> 
> In summary of the attachments, the failure basically goes like this:
> 
> ' Send username and password.
>    ' Send the transaction.
>    udp.Begin
>      Write #udp, id As Byte
>      Write #udp, 50 As Byte
>      Write #udp, credentials As String ' credentials =
> "myusername,mypassword"
>    udp.Send
> 
> ' Read the username and password.
>    id = Read #udp As Byte
>    type = Read #udp As Byte
>    If Eof(udp) = False Then data = Read #udp, Lof(udp) ' Username and
> password separated elsewhere, not a problem.
> 
> data should be "myusername,mypassword" but it actually is
> "^Uanon at ...2571...,mypassword". "\x15" prepends the string, strangely. I
> think this errant byte also precedes any number of datatypes that are
> send separately and later read as a single string. What is this byte,
> and how may I get rid of it?

Not strange if you read the doc carefully. :-)

When using "WRITE #Stream, AString As String", the length of the string is 
always written before the string contents.

To just write the string contents, you must use the second syntax of WRITE:

	WRITE #Stream, String, Length

-- 
Benoît Minisini