UseHalfClose property

Type: Boolean

Indicates whether HexTcpQuery should use a TCP half-close after sending a query. You should set this property before calling one of the query methods. The default value is the value of the UseHalfClose registry setting, or false if the registry setting is not present.

The TCP half-close is a transport-level signal that indicates the client has finished sending its query. If you turn off the half-close, you must send an application-level signal to indicate your query is finished (which you should do anyway). This typically means ending your query strings with a CRLF (or two CRLFs, in the case of HTTP).

This option is provided to control interoperability with various server implementations. Some rare (and broken) implementations do not respond correctly to the TCP half-close. In particular, the Whois software that RIPE updated in 2001 at whois.ripe.net intentionally mishandles the half-close, supposedly in an effort to improve security.

The only known issue with leaving the half-close off is that you must terminate your queries as described above. If you don't, the server you're querying will not know you're finished and will continue waiting, causing HexTcpQuery to time out.