FF hex code not sending properly, from phone to computer and vise versa

When I send FF hex code, it change to 7F or a bunch of symbols. However when I use other values it work normally. Why is this the case and how to fix it, thank you in advance.

Show us your blocks and your sketch.

This is not from MQTT it from TCP. Both have the same issue and the same block the only difference is the MQTT protocol .

For both MQTT and TCP when I receive or transmit it show up like the image , or I get back 7F but not FF.

The sketch is an .ino file, right?

This looks suspicious.

What is the point of setting something to its own current value?

Maybe you wanted true or false?

Sorry what do u mean by ino.file

Do u mean when I put true it will allow hex code and false it won't?
Btw I don't need to set it value, I place it there because I was following someone else code.

Maybe you could post a link to the documentation for that block?