Python chat program GUI using custom Tkinter crashing/not responding

Question

In this part of my code, when a button is clicked, to host the connection, it gets the nickname and then establishes a socket, which is listening for connections.

def establish_host_connection():
    global public_key_of_partner
    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    HOSTIP = socket.gethostbyname(socket.gethostname())
    server.bind((HOSTIP, 9099))
    server.listen()
    client, _ = server.accept()
    print('connected')

    client.send(public_key.save_pkcs1("PEM"))
    public_key_of_partner = rsa.PublicKey.load_pkcs1(client.recv(1024))
    print('Connected')

def host_button_click_event():
    Nickname = ctk.CTkInputDialog(text="Enter Nickname:", title="Nickname")
    Nickname.get_input()
    
    establish_host_connection()

After entering the nickname the interface stops responding and crashes. I have no idea why. Please help: I need to complete this as an assignment.