TCPListener

The TCPListener class allows you to create and configure a TCP server in 4D. Once the TCP listener is instantiated, you can receive client TCP connections and communicate using any protocol supporting TCP.

History

Release	Changes
20 R9	Class added

The TCPListener class is available from the 4D class store. You can create a TCP server using the 4D.TCPListener.new() function, which returns a TCPListener object.

All TCPListener class functions are thread-safe.

Aynchronous programming

This class supports asynchronous programming in 4D as described in the Asynchronous Execution page.

Example

property listener : 4D.TCPListener

Class constructor($port : Integer)
	
	This.listener:=4D.TCPListener.new($port; This)
		
Function terminate()
	
	This.listener.terminate()
	
Function onConnection($listener : 4D.TCPListener; $event : 4D.TCPEvent)->$result
    	//when connected, start a server to handle the communication
	If($event.address # "192.168.@") 
		$result:=Null //in some cases you can reject the connection
	Else
		$result:=cs.MyAsyncTCPConnection.new(This) //see TCPConnection class
	End if
	
Function onError($listener : 4D.TCPListener; $event : 4D.TCPEvent)
	
Function onTerminate($listener : 4D.TCPListener; $event : 4D.TCPEvent)

note

See example in TCPConnection class for a description of the MyAsyncTCPConnection user class.

TCPListener Object

A TCPListener object is a shared object.

TCPListener objects provide the following properties and functions:

errors : Collection a collection of error objects associated with the connection
port : Number the port number of the machine
.terminate() closes the listener and releases the port

4D.TCPListener.new()

4D.TCPListener.new( port : Number ; options : Object ) : 4D.TCPListener

Parameter	Type		Description
port	Real	->	TCP port to listen
options	Object	->	Configuration options for the listener
Result	4D.TCPListener	<-	New TCPListener object

Description

The 4D.TCPListener.new() function creates a new TCP server listening to the specified port using the defined options, and returns a 4D.TCPListener object.

options parameter

In the options parameter, pass an object to configure the listener and all the TCPConnections it creates:

Property	Type	Description	Default
onConnection	Formula	Callback when a new connection is established. The Formula receives two parameters ($listener and $event, see below) and must return either null/undefined to prevent the connection or an option object that will be used to create the TCPConnection.	Undefined
onError	Formula	Callback triggered in case of an error. The Formula receives the TCPListener object in $listener	Undefined
onTerminate	Formula	Callback triggered just before the TCPListener is closed. The Formula receives the TCPListener object in $listener	Undefined

Callback functions

Callback functions receive up to two parameters:

Parameter	Type	Description
$listener	TCPListener object	The current TCP listener instance.
$event	TCPEvent object	Contains information about the event.

Sequence of Callback Calls:

1. onConnection is triggered each time a connection is established.
2. onError is triggered if an error occurs.
3. onTerminate is always triggered just before a connection is terminated.

TCPEvent object

A TCPEvent object is returned when a callback function is called.

.errors

errors : Collection

Description

The .errors property contains a collection of error objects associated with the connection. Each error object includes the error code, a description, and the signature of the component that caused the error.

Property		Type	Description
errors		Collection	4D error stack in case of error
	[].errCode	Number	4D error code
	[].message	Text	Description of the 4D error
	[].componentSignature	Text	Signature of the internal component which returned the error

.port

port : Number

Description

The .port property contains the port number of the machine. This property is read-only.

.terminate()

.terminate()

Parameter	Type		Description
			Does not require any parameters

Description

The terminate() function closes the listener and releases the port.