T_HSOCKET

Variables of this type represent a connection handle or a handle of an open socket. Via this handle, data can be sent to or received from a socket. The handle can be used to close an open socket.

Syntax

TYPE T_HSOCKET
STRUCT
    handle     : UDINT;
    localAddr  : ST_SockAddr; (* Local address *)
    remoteAddr : ST_SockAddr; (* Remote endpoint address *)
END_STRUCT
END_TYPE

Values

Name	Type	Description
handle	UDINT	Internal TwinCAT TCP/IP Connection Server socket handle.
localAddr	ST_SockAddr	Local socket address.
remoteAddr	ST_SockAddr	Remote socket address.

The following sockets can be opened and closed via the TwinCAT TCP/IP Connection Server: Listener socket, Remote Client socket or Local Client socket. Depending on which of these sockets was opened by the TwinCAT TCP/IP Connection Server, suitable address information is entered into the localAddr and remoteAddr variables.

Connection handle on the server side

The function block FB_SocketListen opens a listener socket and returns the connection handle of the listener socket.
The connection handle of the listener sockets is transferred to the function block FB_SocketAccept. FB_SocketAccept will then return the connection handles of the remote clients.
The function block FB_SocketAccept returns a new connection handle for each connected remote client.
The connection handle is then transferred to the function blocks FB_SocketSend and/or FB_SocketReceive, in order to be able to exchange data with the remote clients.
A connection handle of a remote client that is not desirable or no longer required is transferred to the function block FB_SocketClose, which closes the remote client socket.
A listener socket connection handle that is no longer required is also transferred to the function block FB_SocketClose, which closes the listener socket.

Connection handle on the client side

The function block FB_SocketConnect returns the connection handle of a local client socket.
The connection handle is then transferred to the function blocks FB_SocketSend and FB_SocketReceive, in order to be able to exchange data with a remote server.
The same connection handle is then transferred to the function block FB_SocketClose, in order to close a connection that is no longer required.

The function block FB_SocketCloseAll can be used to close all connection handles (sockets) that were opened by a PLC runtime system. This means that, if FB_SocketCloseAll is called in one of the tasks of the first runtime systems (port 801), all sockets that were opened in the first runtime system are closed.

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)