Hi,
dont let my reputation fool you, I am new to freelancer but I am highly experienced software engineer. My speciality is IoT and I implemented xmpp protocol on many platforms. I have done implementations of xmpp clients in java and in C. I think that I will be perfect candidate for the job.
You will also need a xmpp server running on public IP address, I recommend openfire.
If you agree I can make a demo app before you make a decision about hiring and if you like what I made then you can hire me.
Best regards,
ZMI