I am not a programmer, I have been handed this by the programmer as a network fault, so please bear with me while I try to explain.
We are using Chilkat_9_5_0.Http with OAuth without going through a proxy.
The key part of the code: (as best I can tell) is:
loReq = CreateObject("Chilkat_9_5_0.HttpRequest")
loreq.AddHeader(" connectionID ", "aaaaaaaa-bbbb-cccc-ddd-eeeeeeeeeeeeee")
loReq.HTTPVerb = "GET"
loReq.Path = " a-path-in-here "
loReq.ContentType = "text/xml"
loResp = loHTTP.SynchronousRequest("https://**URL-HERE**", 443, 1, loReq)
On W7-64 we don't have an issue. With XP, the connection fails when using a URL rather than an IP address in the line beginning loResp. Using Wireshark, I can see the connection is attempted, to the correct IP address, but via UDP rather than TCP.
loResp = loHTTP.SynchronousRequest("IP-HERE", 443, 1, loReq) - connection works
loResp = loHTTP.SynchronousRequest("https://URL-HERE", 443, 1, loReq) - connection fails
If there is any info I have missed out that would be useful, please let me know.