I mean, can I expect to work
POST / HTTP/1.1
Content-Type: application/octet-stream
Content-Length: 27
[27 bytes of binary data]
And the binary data is arbitrary binary data, not Base64 encoded with all 8 bits in use, not 7 bits. The receiving application is custom application that would know what to do with the data.
Of course, I could test, but I need to know if this is likely to work with real server and over web, not just between both client and server running on a localhost.