Deassigns (releases) an I/O channel previously acquired using the Assign I/O Channel ($ASSIGN) service. Related Functions The equivalent Sockets API function is close(). Format SYS$DASSGN chan C Prototype int sys$dassgn (unsigned short int chan); Returns OpenVMS usage:cond_value type: longword (unsigned) access: write only mechanism: by value Longword condition value. All system services return (by immediate value) a condition value in R0. Condition values that can be returned by this service are listed under Condition Values Returned.
1 – Arguments
chan OpenVMS usage:channel type: word (unsigned) access: read only mechanism: by value Number of the I/O channel to be deassigned. The chan argument is a word containing this number.
2 – Description
After all communication is completed, use the $DASSGN system service to free an I/O channel. A $DASSGN operation executed on a channel associated with a network pseudodevice does the following: o Ends all pending operations to send or receive data at $QIO level ($CANCEL system service). o Clears the port associated with the channel. When executing the $DASSGN system service for TCP sockets, the socket remains until the connection is closed on both the local and remote sides. o Ends all communications with the network pseudodevice that the I/O channel identifies. o Frees the channel associated with the network pseudodevice. An I/O channel can be deassigned only from an access mode equal to or more privileged than the access mode from which the original channel assignment was made. I/O channels assigned from user mode are automatically deassigned at image exit. NOTE Even after a $DASSGN has been issued, a TCP socket may remain until the TCP close timeout interval expires. The default and maximum timeout interval is either 10 minutes if the peer host is not responding or 30 seconds after acknowledging the socket close. Although the TCP socket is open, you cannot make a reference to that socket after issuing a $DASSGN.
3 – Condition Values Returned
SS$_NORMAL The service completed successfully. SS$_IVCHAN An invalid channel number was specified (that is, a channel number of zero or a number larger than the number of channels available). SS$_NOPRIV The specified channel is not assigned or is assigned from a more privileged access mode.