Your question as posted in the title is not worth answering IMO, because I suspect it's one roundabout attempt to solve the root problem that just begets more unsolved problems.
I can't connect to this module via serial port to configure ...
Can you connect to this module through its serial port from a PC?
If you cannot communicate with this module over its serial port, then doesn't that defeat the purpose of this module, and render it useless?
The user manual for that module states
2.3.3 Command Mode of Serial
Module also provides the command mode based on serial control, which is different from auto-work mode, this
mode provides the user with sufficient flexibility, and meet users’
specific needs of different applications. In this mode, the module
works according to user command through the serial, user can control
the module completely with the command, including modifying
parameters, controling networking, controling TCP/IP connection and
Seems like the solution to the root problem involves figuring out (i.e. reading the manual on) how to activate this command mode through the module's serial port. Some familiarity with the structure of the AT command format (based on the old Hayes dial-up modem command set) would help to understand the sparse manual. Perhaps the vendor can supply a GUI or command line interface for the serial port (there are numerous screen captures of a UART-WIFI Configuration program that seems distinct from the web interface); otherwise you can write your own interface program or else (as last resort) use a terminal emulator (e.g. putty or teraterm or Hyperterminal(yuck), or minicom for linux) to manually type the AT commands.
Or is there any other solution for this problem ?
After skimming the user manual, the simple answer is that you need to download and install the "Wifi software", which is the UART-WIFI Configuration program. That appears to be a Windows GUI program that connects to the module through the serial port (ref 184.108.40.206 Management through serial connection), and allow module configuration changes, including a restore to factory settings.
Further review of the user manual indicates that this module has a peculiar implementation of the Hayes AT command set. In particular:
Instead of "AT" commands, it is really "AT+" commands. The null command does require the plus character. All commands begin with the three characters "AT+".
The default escape time is 2 seconds, not the more common 1 second. In order to escape (data) transmission mode, no data or text can be sent to the serial port for 2 seconds, then three "+" (plus) characters must be sent, and then no data or text for 2 seconds. The module should then respond with the "+OK" command prompt.