Non-ASCII characters are replaced with octal escape sequences.
Thanks Tim, this is a great hint.
I feel I will need to dig much deeper into multipart encoding again. Currently, our HTTP client code sends ASCII bodies unchanged. This was implemented under the assumption is that input like…
<xml>\101</xml>
...would be adopted unchanged by the server. However, as it seems, the OxGarage TEI web service will unescape the body and interpret it as <xml>A</xml>.
I think I’m asking too much, but have you possibly spent more time on this? My instantaneous searches and RFC lookups for octal encoding in multipart form data haven’t been that successful.