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johnny_skunk
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Joined: 21 Sep 2005
Posts: 9
Location: Austin, TX
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 Posted: Sep 21st, 2005 03:07 PM Post subject: winsock(AX not API) memory leak ? |
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i've been trying to create a multi-client/single server messenger for quite some time, and every time i run into the same damned problem.
the problem is not that i don't know how to code it, it's that when i have a client connected and the client sends 2 messages in a short period of time, they overlap eachother... heres an example:
the format of my message is as follows
[$timestamp/$command/$command_data]
no say they are sending to chat, which is the command.. and the data is the message; if they type too fast, or send a message twice i get:
[$timman$dat.... it's all compiled into one message, truncating part of each message they sent.
anyone have any clue as to why this happens.. or even what i'm talking about?
thanks
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dougthomas
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Joined: 27 Jul 2005
Posts: 271
Location: Essex, UK
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| Posted: Sep 22nd, 2005 10:54 PM Post subject: |
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Hi Johnny,
I suspect your problem may be that you're not waiting for the previous send to complete before allowing the client to issue another one.
The SendComplete event triggers when a message has been sent. It's like the opposite of DataArrival. I'm sure that there's a better way of doing it but I use something like:
| Code: |
Public boSent as boolean
Private Sub SendToServer(strMessage)
boSent = False
wsock.SendData strMessage
'
' SendComplete event sets boSent = True
' when the message has been sent
'
Do Until boSent = True
Doevents
Loop
End Sub
Private Sub wsock_SendComplete()
boSent = True
End Sub
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You do run the risk that if, for some reason, the SendData doesn't complete the Client is stuck in a loop until he / she takes some action so it may be more apprpriate to start a timer immediately before the Send and if the timer expires, timeout the send.eg
| Code: |
Public boSent as Boolean
Public boTimedOut as Boolean
Private Sub SendToServer(strMessage)
boSent = False
boTimedOut = False
Timer.Interval = 20000 ' This can be set at Design time or in Form_Load
Timer1.Enabled = True
wsock.SendData strMessage
'
' SendComplete event sets boSent = True
' when the message has been sent
'
Do Until boSent = True or boTimedOut = True
Doevents
Loop
If boTimedOut = True then
MsgBox "Timeout occurred on last transmission to Server - please reconnect"
wsock.close
Timer.Enabled = False
End Sub
Private Sub Timer1_Timer()
boTimedOut = True
End Sub
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Here the client will loop until either the data sends ok or 20 seconds has elapsed - whether 20 seconds is long enough or not, who knows. It depends on the amount of data being transmitted, speed of connection etc etc. In the example above, no recovery action has been attempted and the Client will be disconnected. I've yet to find a way of cancelling a transmission in progress other than disconnecting which seems a bit drastic if the timeout was due, say, to network congestion.
(That well known Law says that transmission completes exactly 1 microsecond after the timeout period has expired)
Of course, you should also have similar code in the server although you can be a bit more clever and assign a boSent flag for each Client and check it for True just before you send data to the client. That way, your server can process requests for other Clients whilst waiting for the message to this Client to complete.
Regards
Doug
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johnny_skunk
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Joined: 21 Sep 2005
Posts: 9
Location: Austin, TX
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| Posted: Sep 24th, 2005 01:42 AM Post subject: |
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cool dude, that does the trick. much appreciated.
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johnny_skunk
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Joined: 21 Sep 2005
Posts: 9
Location: Austin, TX
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| Posted: Sep 24th, 2005 01:59 AM Post subject: |
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how would i establish several connections on the same port. one server, several clients?
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dougthomas
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Joined: 27 Jul 2005
Posts: 271
Location: Essex, UK
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| Posted: Sep 24th, 2005 05:25 AM Post subject: |
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Hi,
Here's one I made earlier.......
| Code: |
Dim intClients as Integer
Private Sub Form_Load()
'
' Initialise constants and establish the Listening Port
'
intClients = 0
wsock(0).Protocol = sckTCPProtocol
wsock(0).LocalPort = 1001
wsock(0).Listen
End Sub
Private Sub wsock_ConnectionRequest(Index As Integer, ByVal requestID As Long)
'
' Someone is trying to connect
' Set-up a socket for them to communicate
' and accept the request
'
intClients = intClients + 1
Load wsock(intClients)
wsock(intClients).Protocol = sckTCPProtocol
wsock(intClients).LocalPort = 0
wsock(intClients).Accept requestID
< here you might send the new client a welcome message>
< or ask for credentials, or whatever>
End Sub
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A word of explanation.....
You need to set-up the listening socket as the first in an arryay of sockets (ie set its Index property to 0)
When a connection request comes through you create another socket element for this connection and accept the request. intClients get incremented each time a socket is added so the next available client socket is intClient + 1.
Regards
Doug
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johnny_skunk
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Joined: 21 Sep 2005
Posts: 9
Location: Austin, TX
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| Posted: Sep 25th, 2005 09:08 PM Post subject: |
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it works, but i'm curious as to why you set the local port as 0? i've never seen that done before.
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dougthomas
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Location: Essex, UK
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| Posted: Sep 26th, 2005 12:44 AM Post subject: |
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Hi,
Doesn't have to be zero, just different from the listening socket.My code was just an example I suppose if you were going to use it in anger you should use TCP well known port numbers where appropriate.
regards
Doug
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ajani
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