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Bo Berglund
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 Posted: Thu Oct 30, 2003 9:45 pm Post subject: TClientSocket problems when connecting to server |
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I have this strange problem:
I have created a class for communicating with a server of our own. It
uses TClientSocket which is created in code. When I use this class in
the test application it works OK but in the big client application it
does not work. The client application is a database app and it has an
ADO connection open to another server where the SQL-Server database
resides.
What happens is this:
First I create the socket: FSocket := TClientSocket.Create(NIL)
Then I set the properties like this:
FSocket.ClientType=nonBlocking
FSocket.Port=something
FSocket.OnConnect, OnDisconnect,OnRead and OnError are set to
handlers.
FSocket.Host is set to the target computer name
Then I have tried both FSocket.Open and FSocket.Active := true.
Both result in a long delay and then the OnError gets fired with an
eeLookup ErrorEvent
The messagetext is: "No such host is known"
But when I use the simple test application using this class the
connection is immediately established running the exact same code....
Also pinging the host in a command window always succeeds.
What should I look out for???
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Remy Lebeau (TeamB)
Guest
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| Posted: Thu Oct 30, 2003 11:03 pm Post subject: Re: TClientSocket problems when connecting to server |
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"Bo Berglund" <bo.berglund (AT) mailbox (DOT) swipnet.se> wrote
| Quote: | Then I have tried both FSocket.Open and
FSocket.Active := true. Both result in a long delay
and then the OnError gets fired with an eeLookup
ErrorEvent The messagetext is: "No such host is known"
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What are you actually setting the Host to? It needs to be a name that is
resolvable via DNS. Otherwise use an IP address with the Address property
instead of Host.
| Quote: | But when I use the simple test application using this class
the connection is immediately established running the
exact same code....
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Ok, so what are the differences between your main app and the test app?
Does the main app has a message queue? How exactly is the socket class
being used by the two apps?
Gambit
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Bo Berglund
Guest
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| Posted: Fri Oct 31, 2003 12:06 am Post subject: Re: TClientSocket problems when connecting to server |
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On Thu, 30 Oct 2003 15:03:25 -0800, "Remy Lebeau (TeamB)"
<gambit47.no.spam (AT) no (DOT) spam.yahoo.com> wrote:
| Quote: | Ok, so what are the differences between your main app and the test app?
Does the main app has a message queue? How exactly is the socket class
being used by the two apps?
Same class handles everything. I just call create on the class and |
then the Connect method giving the host as argument (see below).
Sorry for waisting the bandwidth...
It turned out that the main app retrieved the host name from the
database (inside a config string) and earlier today the string parsing
had been "fixed" to solve another problem. But it introduced a new bug
so that my actual hostname string became '=host' instead of 'host'.
And this was hidden in my logfiles as well because the host is logged
but the extra = in the log did not show clearly enough. It combined
with the normal = in the log to form a slightly longer ==. I use
Lucida Console font in the editor I examine logs with and this font
melts these two together with no space inbetween....
I have struggled 3-4 hours with this one without getting close to what
was wrong. Sigh...
Now its finally time for bed.
/Bo
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Martin James
Guest
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| Posted: Fri Oct 31, 2003 12:16 am Post subject: Re: TClientSocket problems when connecting to server |
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| Quote: | database (inside a config string) and earlier today the string parsing
had been "fixed" to solve another problem. But it introduced a new bug
so that my actual hostname string became '=host' instead of 'host'.
And this was hidden in my logfiles as well because the host is logged
but the extra = in the log did not show clearly enough. It combined
with the normal = in the log to form a slightly longer ==. I use
Lucida Console font in the editor I examine logs with and this font
melts these two together with no space inbetween....
I have struggled 3-4 hours with this one without getting close to what
was wrong. Sigh...
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<g> I find a space at the start of a string to be difficult to spot with the
debugger.
Rgds,
Martin
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hclarius
Guest
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| Posted: Fri Oct 31, 2003 3:33 am Post subject: Re: TClientSocket problems when connecting to server |
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Bo Berglund wrote:
| Quote: | I have this strange problem:
I have created a class for communicating with a server of our own. It
uses TClientSocket which is created in code. When I use this class in
the test application it works OK but in the big client application it
does not work. The client application is a database app and it has an
ADO connection open to another server where the SQL-Server database
resides.
What happens is this:
First I create the socket: FSocket := TClientSocket.Create(NIL)
Then I set the properties like this:
FSocket.ClientType=nonBlocking
FSocket.Port=something
FSocket.OnConnect, OnDisconnect,OnRead and OnError are set to
handlers.
FSocket.Host is set to the target computer name
Then I have tried both FSocket.Open and FSocket.Active := true.
Both result in a long delay and then the OnError gets fired with an
eeLookup ErrorEvent
The messagetext is: "No such host is known"
But when I use the simple test application using this class the
connection is immediately established running the exact same code....
Also pinging the host in a command window always succeeds.
What should I look out for???
|
Let me apologize if I am missing something but,
if you just want to connect and interact with SQL Server on an internal
server, why are you using Sockets and ADO? Just use ADO.
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Bo Berglund
Guest
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| Posted: Fri Oct 31, 2003 6:31 am Post subject: Re: TClientSocket problems when connecting to server |
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On Thu, 30 Oct 2003 19:33:09 -0800, hclarius
<hfclarius (AT) nospamcomcast (DOT) net> wrote:
| Quote: |
Let me apologize if I am missing something but,
if you just want to connect and interact with SQL Server on an internal
server, why are you using Sockets and ADO? Just use ADO.
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You *are* missing something 
The sockets connection is to a special PC that handles control of a
scanning device. This device must be controlled from several different
client computers on the network. The config data for this device is in
a common SQL database accessed by all clients, from the config string
in the database the PC name and the connection TCP port are extracted.
So the client needs access to the SQL db (via ADO) and then the
scanner server via sockets.
The reason I mentioned ADO was that to my mind this was the only real
difference between the real client software and the socket
communications test program. The ADO connection is done through
TCP/IP, not pipes, so there was a remote possibility for some kind of
interplay here.
However, as usual, the real reason was a *bug* in the decoding
function for the config string retrieved from the database. (Described
in another reply.) The test application of course has edit boxes for
manual entry of these parameters and the data are always right....
/Bo
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