HexTcpQuery registry settings

HexTcpQuery provides a way of changing special options though the Windows registry.

If it does not already exist, create the following registry key:


Then you can create one or more of the following values below it:

UseHalfClose (DWORD)

Set this value to 1 to turn on the TCP half-close option, 0 to turn it off. The TCP half-close is off by default as of version 1.0.19.

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.

MaxBufferSize (DWORD)

Set this value to the maximum number of bytes to allocate for HexTcpQuery's receive buffer. The default is 1,048,576 (1 MB).

HexTcpQuery is not designed for receiving large files--it stores everything it receives in memory before passing it back as a return value. This makes the programming interface very simple but limits the amount that can be received. If you want to receive multi-megabyte files, you should consider using a regular socket component, HTTP component, or FTP component that allows you to receive and save files in a series of chunks.

Nevertheless, if you want to receive large files with HexTcpQuery and have sufficient RAM to devote to the task, you can raise HexTcpQuery's receiving limit by setting this registry value.

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