Sorry but there are not many psychics here.
You retrieve a text file from.. where, by what kind of communication? Serial, Wifi, is a file on a SD... can you provide even fewer clues than you did?
Who is sending what, how, to whom? Communication means someone tries to makes itself understood by providing relevant context.
Where is setup, where is loop? Or are you talking about a secret library you-re trying to use and want to keep it secret?