Reasons of gibberish are as below:

1.The setting of baud rate, data bits, check bit are not matched between serial device any our converter.

2. Hardware
Serial TTL RS232 RS485, they are different level types, cannot be connected directly. Need to be converted via 232 or 485 chip. It is wrong to link TTL to PC since PC is RS232 level. Besies, poorly designed hardware will bring interference then cause abnormal communication. If you cannot confirm where is the problem, exclude through sending and receiving.

1. Make device and computer communicate directly,and set baud rate and so on as you understand. See whether it works well.
2. Disconnect your device and module and short RXD and TXD. Then send and receive via internet to see the data.
3. Disconnect your device and module and short RXD and TXD. Then send , receive via computer to check the working.