FB_SocketListen

Using the function block FB_SocketListen, a new listener socket can be opened via the TwinCAT TCP/IP Connection Server. Via a listener socket, the TwinCAT TCP/IP Connection Server can 'listen' for incoming connection requests from remote clients. If successful, the associated connection handle is returned at the hListner output. This handle is required by the function block FB_SocketAccept. If a listener socket is no longer required, it can be closed with the function block FB_SocketClose. The listener sockets on an individual computer must have unique IP port numbers.

Inputs

VAR_INPUT
    sSrvNetId   : T_AmsNetId := '';
    sLocalHost  : T_IPv4Addr := '';
    nLocalPort  : UDINT;
    bExecute    : BOOL;
    tTimeout    : TIME := T#5s;
END_VAR

Name	Type	Description
sSrvNetId	T_AmsNetId	String containing the network address of the TwinCAT TCP/IP Connection Server. For the local computer (default) an empty string may be specified.
sLocalHost	T_IPv4Addr	Local server IP address (Ipv4) in the form of a string (e.g. '172.13.15.2'). For a server on the local computer (default), an empty string may be entered.
nLocalPort	UDINT	Local server IP port (e.g. 200).
bExecute	BOOL	The function block is enabled by a positive edge at this input.
tTimeout	TIME	Maximum time allowed for the execution of the function block.

Outputs

VAR_OUTPUT
    bBusy      : BOOL;
    bError     : BOOL;
    nErrId     : UDINT;
    hListener  : T_HSOCKET;
END_VAR

Name	Type	Description
bBusy	BOOL	This output is active if the function block is activated. It remains active until acknowledgement.
bError	BOOL	If an error should occur during the transfer of the command, then this output is set once the bBusy output was reset.
nErrId	UDINT	If an bError output is set, this parameter returns the TwinCAT TCP/IP Connection Server error number.
hListener	T_HSOCKET	Connection handle to the new listener socket.

Requirements

Development environment	Target system type	PLC libraries to include (category group)
TwinCAT v3.1.0	PC, or CX (x86, X64, Arm®)	Tc2_TcpIp (communication)