Multiple Connection (Winsock)

Hello everyone there,

I got couple of questions to ask regarding winsock connection.

1. I have come across the use of control array for multiple client connection to the server, so need you guys to enlighten me in this area.

Can I know how does actually the following codes works in allowing for multiple connection from Client?
What I understand - if there is already an existing connection made by one client, the code will create another new array of sockets, but why is it necessary to put if index is 0?
And for the last line in the procedure, I notice that each time I Close a connection from the client and connect again from the same client, the Client Port increase by 1, for example: before close 1065 but after close and connect, I got 1066, now why does the port number increase by 1 and what it means actually?

Notes: Some of this codes i picked up from internet.


Option explicit
Dim iSockets as Integer

Private Sub WinsockServer_ConnectionRequest(Index As Integer, ByVal requestID As Long)
If Index = 0 Then
iSockets = iSockets + 1
Load WinsockServer(iSockets)
WinsockServer(iSockets).LocalPort = 1001
WinsockServer(iSockets).Accept requestID
End If
End Sub

What about the following codes for to take care of the closing?


Private Sub WinsockServer_Close(Index As Integer)
WinsockServer(Index).Close
Unload WinsockServer(Index)
iSockets = iSockets - 1
End Sub


2.When I only have one Client and one host, how can I close the connection and reconnect again when needed. I have the following code with me but got one problem, after closing the connection it just refuse to reconnect again? Do I really need to use control array to do this? Is there any other way?

Following is server program:


Private Sub Form_load()
WinsockServer.LocalPort = 1001
WinsockServer.Listen
End Sub


Private Sub Form_Unload(Cancel As Integer)
WinsockServer.Close
End Sub

Private Sub WinsockServer_ConnectionRequest(ByVal requestID As Long)
If WinsockServer.State <> sckClosed Then
WinsockServer.Close
End If
WinsockServer.Accept requestID
End Sub


And the following are Client program:


Private Sub Form_load()
tcpClient.RemoteHost = "127.0.0.1"
tcpClient.RemotePort = 1001
End Sub

Private Sub cmdConnect_Click()
Dim strnow As Long
If tcpClient.State <> sckClosed Then
tcpClient.Close
Do Until tcpClient.State = sckClosed
DoEvents
Loop
End If
tcpClient.Connect

strnow = Timer 'read current time b4 entering the loop
Do While (tcpClient.State <> sckConnected)
DoEvents
If (Timer - strnow) > 3 Then 'prevent endless loop
Exit Sub
End If
Loop
End Sub


3. Can anyone tell me how can I use object.localport = 0? I understand that this allow for random assign port number instead of using a specific one however I failed to connect my client to the server by using the following code:

For server, I have
WinsockServer.LocalPort = 0
And for client, I have
TcpClient.LocalPort = 0


I guess that is all for now, sorry for the long question ;)

Answers to your questions:


Yes, all is well and good except for one line:

WinsockServer(iSockets).LocalPort = 1001

Two winsocks can not have the same LocalPort, you will get an Address In Use error, I suggest this:

WinsockServer(iSockets).LocalPort = 1000 + iSockets
I have no idea, looks like it should work, you might want to increase the value of this, so it waits longer:

If (Timer - strnow) > 30 Then 'prevent endless loop
I suspect the problem is that the server is given a random port number, so the client doesnt know which port to connect to. You should try a fixed or semi-fixed (with a range of values) LocalPort that the clients connect to, and then any new winsocks which actually accept the connection can be made random.


And a side note, there are tags and for putting code into posts :)

2. - I dont see any disconnect code, but basically, when the server connection is closed, you need to reset the socket.
Add a timer, and check the state of the socket every minute or so.
Sub Timer1_Timer()
If WinsockServer.State <> sckConnected Then
WinsockServer.Close
WinsockServer.Listen
End If
End Sub

3. Random port assigning is normally done with a control array. You will have one control array, and one normal sock. The normal one wil listen on a certain port, and in its connection_request event, it will load a new sock in the control array and accept the request on that. Windows will automatically assign the new sock a randomly found localport to receive the connection on.

Ahh. I really want to create a Login Program Like the ones in YM and other MMORPG that will sign out the Account of the user if he/she Login on another Computer.. Please Help.. Thnxxx