7.15.6 TDISCON

TDISCON (disconnect the specified connection)

Function

• TDISCON system library is used to asynchronously disconnect the current TCP connection

Set up and establish communication connections

• After the user configures the correct IP address and port number in the connect block, set the REQ parameter to true to enable the disconnection function and terminate the current communication connection.

• The disconnect function only works when the communication connection has been successfully established

• The correct disconnection process requires giving the req pin a rising edge first. You can see that the status word in the TDISCON block changes from 0x7003 (terminating the connection) → 0x7007 (the connection has been terminated), indicating that the connection has been successfully disconnected.

• After the connection is established, if the peer actively disconnects at this time, the status code will change from 0x7004 (already established) → 0x7002 (connection is being established); if the connection is disconnected at this time, the socket resources created by the party will be released. RST messages can be seen through packet capture; if one is the server, one will also be removed from the listening state, and the other party will no longer be able to establish a connection in the future.

LD graphics

Parameter description

Interface Variables	Declaration	Data Type	Description
REQ	Input	BOOL	Proactively disconnect only when rising edge is recognized
CONNECT	InOut	TCP_ConnectConfig	Function block instance for configuring connection parameters, refer to TCP_Connectconfig
DONE	Output	BOOL	State parameter with the following possible values: 0: The disconnection function has not been started or is still in progress 1: The disconnection function has been successfully executed. This status will only show for one cycle
BUSY	Output	BOOL	State parameter with the following possible values: 0: The disconnection function has not yet started or has been completed 1: The disconnection function has not yet been completed
ERROR	Output	BOOL	State parameter with the following possible values: 0: No error 1: Error in disconnect function
STATUS	Output	WORD	The status of the current function execution process

Status code description

STATUS (WORD 16#)	Description
0000	Uncalled
7003	Communication establishment is closing
7007	Active disconnection

The following are exception status codes	Description
8087	Failed to remove the Epoll Event corresponding to the client
80A2	Active disconnection failed
80AC	Asynchronous function enqueue failed

Example

• LD example is shown in the following animation:

• ST example is shown in the following code:

TDISCON_1(
    REQ:=Close,
    CONNECT:=TCP_CONNECTCONFIG_1,
    DONE=>OUT,
    BUSY=>OUT2,
    ERROR=>OUT3,
    STATUS=>OUT4
);