System.Net.Socket.TSocket.Listen

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Delphi

procedure Listen(const Address, Service: string; Port: Word; QueueSize: Integer = -1); overload;
procedure Listen(const Endpoint: TNetEndpoint; QueueSize: Integer = -1); overload;

C++

void __fastcall Listen(const System::UnicodeString Address, const System::UnicodeString Service, System::Word Port, int QueueSize = 0xffffffff)/* overload */;
void __fastcall Listen(const TNetEndpoint &Endpoint, int QueueSize = 0xffffffff)/* overload */;

Properties

Type	Visibility	Source	Unit	Parent
procedure function	public	System.Net.Socket.pas System.Net.Socket.hpp	System.Net.Socket	TSocket

Description

Configures the socket to begin accepting incoming connections.

After you call Listen, you must call Accept to actually accept an incoming connection and establish a communication channel with that client.

To specify the endpoint where your socket listens, you must provide either of the following combinations of parameters:

• An endpoint (Endpoint).
• An IP address (Address) and a service (Service). You may pass an empty word as Port, as Service is used to determine the port.
• An IP address (Address) and a port (Port). Pass an empty string as Service, otherwise the specified service name is used to determine the port to use, and the specified port is ignored.

QueueSize determines the maximum length of the queue of pending connections. See listen function in the MSDN. Use -1 for the maximum recommended length of the queue (default).

Exceptions

A call to Bind can raise any of the following exceptions:

Exception	Exception.Message	Scenarios
ESocketError	Can't create new socket	Windows failed to create a socket of the requested type. See socket function (MSDN) for more information.
	Can't listen on an open socket	You cannot listen on a socket that is already open. A previous call to any of the following methods must have opened the socket already: Bind Connect Create (if you specify a socket handle and a socket address) GetClientSocket Listen ListenBroadcast OpenBroadcast
	Network socket error: <error message> (<error code>), on API 'bind'	The operating system reported an error while binding your socket to a local IP address. This can only happen if the type of socket is UDP. For more information, see the following documentation for the operating system where your application was running: Windows: bind function (MSDN) OS X: bind (OS X Man Pages) iOS: bind (iOS Manual Pages) Android: bind (Linux Programmer's Manual) Linux: bind (Linux Programmer's Manual)
	Network socket error: <error message> (<error code>), on API 'listen'	The operating system reported an error while configuring your socket to listen for incoming connections. This can only happen if the type of socket is not UDP. For more information, see the following documentation for the operating system where your application was running: Windows: listen function (MSDN) OS X: listen (OS X Man Pages) iOS: listen (iOS Manual Pages) Android: listen (Linux Programmer's Manual) Linux: listen (Linux Programmer's Manual)
	Network socket error: <error message> (<error code>), on API 'socket'	The operating system reported an error while creating a socket. For more information, see the following documentation for the operating system where your application was running: Windows: socket function (MSDN) OS X: socket (OS X Man Pages) iOS: socket (iOS Manual Pages) Android: socket (Linux Programmer's Manual) Linux: socket (Linux Programmer's Manual)

See Also

• System.Net.Socket.TSocket.Accept

• System.Net.Socket.TNetEndpoint
• System.Net.Socket.TSocket.LookupService

• System.Net.Socket.TSocket.ListenBroadcast

• System.Net.Socket.TSocket.CreateSocket
• System.Net.Socket.TSocket.DoBind

• listen function