TCPConnection

The TCPConnection class allows you to manage Transmission Control Protocol (TCP) client connections to a server, enabling you to send and receive data, and handle connection lifecycle events using callbacks.

The TCPConnection class is available from the 4D class store. Puede crear una conexión TCP utilizando la función 4D.TCPConnection.new() que devuelve un TCPConnection object.

All TCPConnection class functions are thread-safe.

Thanks to the standard 4D object refcounting, a TCPConnection is automatically released when it is no longer referenced. Consequently, the associated resources, are properly cleaned up without requiring explicit closure.

TCPConnection objects are released when no more references to them exist in memory. This typically occurs, for example, at the end of a method execution for local variables. If you want to "force" the closure of a connection at any moment, nullify its references by setting them to Null.

Historia

Lanzamiento	Modificaciones
20 R8	Clase añadida

Ejemplos

The following examples demonstrate how to use the 4D.TCPConnection and 4D.TCPEvent classes to manage a TCP client connection, handle events, send data, and properly close the connection. Both synchronous and asynchronous examples are provided.

Synchronous Example

This example shows how to establish a connection, send data, and shut it down using a simple object for configuration:

var $domain : Text := "127.0.0.1"
var $port : Integer := 10000
var $options : Object := New object() // Configuration object
var $tcpClient : 4D.TCPConnection
var $message : Text := "test message"

// Open a connection
$tcpClient := 4D.TCPConnection.new($domain; $port; $options)

// Send data
var $blobData : Blob
TEXT TO BLOB($message; $blobData; UTF8 text without length)
$tcpClient.send($blobData)

// Shutdown
$tcpClient.shutdown()
$tcpClient.wait(0)

Ejemplo asincrónico

This example defines a class that handles the connection lifecycle and events, showcasing how to work asynchronously:

// Class definition: cs.MyAsyncTCPConnection

Class constructor($url : Text; $port : Integer)
    This.connection := Null
    This.url := $url
    This.port := $port

// Connect to one of the servers launched inside workers
Function connect()
    This.connection := 4D.TCPConnection.new(This.url; This.port; This)

// Disconnect from the server
Function disconnect()
    This.connection.shutdown()
    This.connection := Null

// Send data to the server
Function getInfo()
    var $blob : Blob
    TEXT TO BLOB("Information"; $blob)
    This.connection.send($blob)

// Callback called when the connection is successfully established
Function onConnection($connection : 4D.TCPConnection; $event : 4D.TCPEvent)
    ALERT("Connection established")

// Callback called when the connection is properly closed
Function onShutdown($connection : 4D.TCPConnection; $event : 4D.TCPEvent)
    ALERT("Connection closed")

// Callback called when receiving data from the server
Function onData($connection : 4D.TCPConnection; $event : 4D.TCPEvent)
    ALERT(BLOB to text($event.data; UTF8 text without length))

	//Warning: There's no guarantee you'll receive all the data you need in a single network packet.
	
// Callback called when the connection is closed unexpectedly
Function onError($connection : 4D.TCPConnection; $event : 4D.TCPEvent)
    ALERT("Connection error")

// Callback called after onShutdown/onError just before the TCPConnection object is released
Function onTerminate($connection : 4D.TCPConnection; $event : 4D.TCPEvent)
	ALERT("Connection terminated")

Usage example

Create a new method named AsyncTCP, to initialize and manage the TCP connection:

var $myObject : cs.MyAsyncTCPConnection
$myObject := cs.MyAsyncTCPConnection.new("myURL"; 10000)
$myObject.connect()
$myObject.getInfo()
$myObject.disconnect()

Call the AsyncTCP method in a worker:

CALL WORKER("new process"; "Async_TCP")

Objeto TCPConnection

A TCPConnection object is a non-sharable object.

TCPConnection objects provide the following properties and functions:

closed : Boolean whether the connection is closed
errors : Collection a collection of error objects associated with the connection
noDelay : Boolean whether Nagle's algorithm is disabled (true) or enabled (false)
.send( data : Blob ) sends data to the server
.shutdown() cierra el canal write de la conexión (cliente a servidor)
.wait( { timeout : Real } ) espera hasta que se cierre la conexión TCP o se alcance el timeout especificado

4D.TCPConnection.new()

4D.TCPConnection.new( serverAddress : Text ; serverPort : Number ; options : Object ) : 4D.TCPConnection

Parámetros	Tipo		Descripción
serverAddress	Text	->	Domain name or IP address of the server
serverPort	Integer	->	Port number of the server
options	Object	->	Configuration options for the connection
Resultado	TCPConnection	<-	New TCPConnection object

Descripción

La función 4D.TCPConnection.new() crea una nueva conexión TCP a la serverAddress y serverPort especificados, usando las opciones definidas, y devuelve un objeto 4D.HTTPRequest.

Parámetro options

En el parámetro options, pase un objeto que puede contener las siguientes propiedades:

Propiedad	Tipo	Descripción	Por defecto
onConnection	Formula	Callback triggered when the connection is established.	Indefinido
onData	Formula	Callback triggered when data is received	Indefinido
onShutdown	Formula	Callback triggered when the connection is properly closed	Indefinido
onError	Formula	Callback triggered in case of an error	Indefinido
onTerminate	Formula	Callback triggered just before the TCPConnection is released	Indefinido
noDelay	Boolean	Read-only Disables Nagle's algorithm if true	False

Función callback (retrollamada)

All callback functions receive two parameters:

Parámetros	Tipo	Descripción
$connection	objeto TCPConnection	The current TCP connection instance.
$event	objeto TCPEvent	Contains information about the event.

Sequence of Callback Calls:

1. onConnection is triggered when the connection is established.
2. onData is triggered each time data is received.
3. Either onShutdown or onError is triggered:
   • onShutdown is triggered when the connection is properly closed.
   • onError is triggered if an error occurs.
4. onTerminate is always triggered just before the TCPConnection is released (connection is closed or an error occured).

TCPEvent object

Un objeto TCPEvent es devuelto cuando se llama una función de retrollamada.

.closed

closed : Boolean

Descripción

The .closed property contains whether the connection is closed. Returns true if the connection is closed, either due to an error, a call to shutdown(), or closure by the server.

.errors

errors : Collection

Descripción

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.

Propiedad		Tipo	Descripción
errors		Collection	Pila de error 4D en caso de error
	[].errCode	Number	Código de error 4D
	[].message	Text	Descripción del error 4D
	[].componentSignature	Text	Firma del componente interno que ha devuelto el error

.noDelay

noDelay : Boolean

Descripción

The .noDelay property contains whether Nagle's algorithm is disabled (true) or enabled (false). Esta propiedad es de solo lectura.

.send()

.send( data : Blob )

Parámetros	Tipo		Descripción
data	Blob	->	Data to be sent

Descripción

The send() function sends data to the server. If the connection is not established yet, the data is sent once the connection is established.

.shutdown()

.shutdown()

Parámetros	Tipo		Descripción
			No requiere ningún parámetro

Descripción

La función shutdown()cierra el canal write de la conexión (cliente a servidor) mientras se mantiene abierto el canal read (servidor al flujo del cliente) permitiéndole continuar recibiendo datos hasta que la conexión sea completamente cerrada por el servidor o se produzca un error.

.wait()

.wait( { timeout : Real } )

Parámetros	Tipo		Descripción
timeout	Real	->	Tiempo máximo de espera en segundos

Descripción

La función wait() espera hasta que se cierre la conexión TCP o se alcance el timeout especificado

nota

During the .wait() execution, callback functions are executed, whether they originate from other SystemWorker instances. Puede salir de un .wait() llamando a shutdown() desde una retrollamada.