Error 12007 when uploading files with XUpload

Problem Description

When uploading files with XUpload, an error box comes up containing the following error message:

Sending information to the server failed with error code 12007. Uploading has been aborted.

Solution

This error usually occurs when the Server parameter is prefixed by http://:

Incorrect:
<PARAM NAME="Server" VALUE="http://myserver.com">

To fix the problem, remove the http:// prefix, as follows:

Correct:
<PARAM NAME="Server" VALUE="myserver.com">

This error may also be caused by including all or part of a Script path or port number in the Server parameter:

Incorrect:
<PARAM NAME="Server" VALUE="myserver.com/uploads">
<PARAM NAME="Script" VALUE="uploadscript.asp">

Correct:
<PARAM NAME="Server" VALUE="myserver.com">
<PARAM NAME="Script" VALUE="/uploads/uploadscript.asp">

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Incorrect:
<PARAM NAME="Server" VALUE="myserver.com:8080">
<PARAM NAME="Script" VALUE="uploadscript.asp">

Correct:
<PARAM NAME="Server" VALUE="myserver.com">
<PARAM NAME="Script" VALUE="/uploads/uploadscript.asp">
<PARAM NAME="Port" VALUE="8080">