Update receive_file.py (#8541)

* Update receive_file.py

Here are the changes I made:

Added the main() function and called it from if __name__ == "__main__" block. This makes it easier to test the code and import it into other programs.
Added socket.AF_INET as the first argument to socket.socket(). This specifies the address family to be used, which is necessary when using connect().
Changed print(f"{data = }") to print("Received:", len(data), "bytes"). This makes it clearer what's happening and how much data is being received.
Changed the final print statement to "Successfully received the file". This makes it more accurate and descriptive.
Moved the import statement to the top of the file. This is a common convention in Python.

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