There are a load of problems here, starting with
not containing enough space for the data you are concatenating into it, but more importantly, you aren't using strtok even close to correctly.
Look at the documentation: strtok - C++ Reference
] - it includes an example of how to use it. Throw that code away, and start again once you have read the documents and understand what you are doing, instead of just guessing and hoping for the best!