TcpListen

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Function Block - Creates a new socket by performing the bind and listen operations.

Inputs

Input	Data Type	Range	Unit	Default	Description
Execute	BOOL	0, 1	N/A	No default	On the rising edge, listen for socket connections.
Port	DINT	N/A	User units	No default	The network port to use.
Backlog	DINT	N/A	N/A	No default	The size of the queue for pending connections. If more than Backlog number of connection attempts are made prior to a TcpAccept call, the controller may refuse the connections.

Input

Data Type

Range

Unit

Default

Description

Execute

BOOL

0, 1

N/A

No default

On the rising edge, listen for socket connections.

Port

DINT

N/A

User units

No default

The network port to use.

Backlog

DINT

N/A

No default

The size of the queue for pending connections.

If more than Backlog number of connection attempts are made prior to a TcpAccept call, the controller may refuse the connections.

Outputs

Output	Data Type	Description
Done	BOOL	If TRUE, the command completed successfully.
Error	BOOL	If TRUE, an error has occurred.
ErrorID	DINT	Indicates the error if Error output is TRUE. See the table in File and TCP/IP Function Block ErrorIDs.
ListenID	UDINT	The ID of the new listen socket.

Remarks

This function block uses the default TCP settings.
Use the TcpClose function block to release the socket returned by TcpListen.

Figure 1: TcpListen

FBD Language Example

Not available.

FFLD Language Example

Not available.

IL Language Example

Not available.

ST Language Example

(* TcpListen example *)
CASE StepCounter OF
0:
   Inst_TcpListen(TRUE, 1234, 2);
   StepCounter := StepCounter + 1;
1:
   Inst_TcpListen(TRUE, 1234, 2);
   IF Inst_TcpListen.Done THEN
      MyListenID := Inst_TcpListen.ListenID;
      Inst_TcpListen(FALSE, 0, 0);
      StepCounter := StepCounter + 1;
   END_IF;
END_CASE;