Is that server, where you want to send your data (that Blob) to, controlled by you ? Then you can serialize your variables into that blob using any format you want, a concetenation of name=value pairs or something more verbous and structured (JSON and/or XML are good candidates, ...). You can do that because you know how to deserialize that on server side then where you receive the content of the blob. A 3'rd party can't - you need to comply with what they expect and can handle.
All Magic String functions do work on Blobs and you can use a Blob variable as I/O entry and treat it like a file. JSON you could produce with Output Merge or .NET, XML too - or with XML direct access functions, ...
There's also the Magic buffer manipulation functions for putting stuff into a Blob. From those I would however rather stay away. Those are for friends of machine language and assembler programming ^^
When you put character data into your Blob you should use a Blob ANSI and UTF-8 encode all your character data. Binary and Unicode Blobs might result in some encoding issues but you may never experience those resp. have to deal with that stuff.