TCPClose (Close TCP/IP Communication Port)

The TCPClose function is used to close a TCP/IP socket that has been set up for communication.

Syntax

TCPClose ( TCPSocket )

The following program demonstrates the use of TCPClose.

Public Socket as Long
Const IP_Addr = "1.1.1.1" 'Set the IP address to make a connection to

BeginProg
  Socket = TCPOpen(IP_Addr,5000,100)'Create socket. Socket number typically = 101
  Scan (2,Sec,3,10)
    SerialOut (Socket,"wha-da-ya know?",0,1,0) 'send out a string
  NextScan

  TCPClose (Socket)'Close the socket; this can take up to 200 msec
 
EndProg

Remarks

TCPSocket is the variable returned by the TCPOpen function.

If TCPSocket is negated, TCPClose does not close the socket but instead allows PakBus communication to occur on the socket. This feature allows a socket to be opened first for Serial I/O, perhaps to "log in", and then converts the socket so that it can communicate via PakBus. (Note that if TCPSocket is opened by TCPOpen where IPBuffer is non-zero, the socket is opened for Serial I/O only and not for PakBus.)

TCPClose returns 0 if there is no IP interface (Ethernet or PPP).

If a positive TCPSocket is used, this function waits until the socket is closed and should always return 0. (It can take up to 200 msec to close the socket.)

If a negative TCPSocket is used, this function returns:

Code Description
0 The socket is not open or PakBus is already active on the socket.
1 The socket is successfully converted to PakBus.
3 The socket is waiting for a client to authenticate the socket (when the PakBus/TCP setting is active).
4 A challenge has been issued to the client to authenticate the socket (when the PakBus/TCP setting is active).