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50 lines
2.6 KiB
Text
50 lines
2.6 KiB
Text
{{DISPLAYTITLE:_CONNECTED}}
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The [[_CONNECTED]] function returns the status of a TCP/IP connection handle.
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{{PageSyntax}}
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:{{Parameter|result&}} = [[_CONNECTED]]({{Parameter|connectionHandle&}})
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{{PageDescription}}
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* The handle can come from the [[_OPENHOST]], [[OPENCLIENT]] or [[_OPENCONNECTION]] QB64 TCP/IP functions.
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* Returns -1 if still connected or 0 if connection has ended/failed.
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* Do not rely solely on this function to check for ending communication.
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* Use "time-out" checking as well and [[CLOSE]] any suspect connections.
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* If this function indicates the handle is not connected, any unread messages can still be read using [[INPUT (TCP/IP statement)|INPUT #]] or [[GET (TCP/IP statement)|GET #]].
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* Even if this function indicates the handle is not connected, it is important to [[CLOSE]] the connection anyway or important resources cannot be reallocated.
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{{PageExamples}}
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''Snippet:'' Updating the [[_OPENHOST|_OPENHOST chat program example]] to manage the Users array when users are no longer connected.
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{{TextStart}} '' ''
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{{Cb|FOR...NEXT|FOR}} i = 1 {{Cb|TO}} numclients ' distribute incoming messages to all clients
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{{Cb|IF...THEN|IF}} Users(i) {{Cb|THEN}} ' check for non-existing handle values(rare)
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{{Cb|INPUT (TCP/IP statement)|INPUT #}}Users(i), message$
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{{Cb|IF...THEN|IF}} message$ <> "" {{Cb|THEN}}
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{{Cb|FOR...NEXT|FOR}} p = 1 {{Cl|TO}} numclients
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{{Cb|IF...THEN|IF}} Users(p) {{Cb|THEN}} {{Cb|PRINT (TCP/IP statement)|PRINT #}}Users(p), message$
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{{Cb|NEXT}} p
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{{Cb|END IF}}
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{{Cb|IF...THEN|IF}} {{Cb|_CONNECTED}}(Users(i)) {{Cl|IF...THEN|THEN}}
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n = n + 1 ' new consecutive connected index
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Users(n) = Users(i) ' assign handle value to consecutive index
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{{Cb|ELSE}} : {{Cb|CLOSE}} #(Users(i)): Users(i) = 0 ' close and clear index
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{{Cb|END IF}} ' if connected
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{{Cb|END IF}} ' array handle exist
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{{Cb|NEXT}} i
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numclients = n: n = 0 '' ''
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{{CodeEnd}}
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:The connection routine is added to the [[_OPENHOST|chat program's]] message distribution code to update the User array and close bad connections. The value of the n index does not change for non-existing handles or lost connections, so it will always either match the numclients value or be less. This overwrites lost connection handles. Setting handles to 0 clears upper array indices. After the FOR loop has gone through all of the client users, the number of clients is updated to the value of n and n is reset to 0.
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{{PageSeeAlso}}
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* [[_OPENCONNECTION]]
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* [[_OPENHOST]]
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* [[_OPENCLIENT]]
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* [[_CONNECTIONADDRESS$]]
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* [[Downloading Files]]
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{{PageNavigation}}
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