input: Write a python function to create a basic TCP server that listens on a given port and sends a welcome message to clients.
  assert start_server(12345) == "Server started and listening on port 12345"
  assert start_server(54321) == "Server started and listening on port 54321"
  assert start_server(9999) == "Server started and listening on port 9999"
output: import socket
  
  def start_server(port):
      server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
      server_socket.bind(('0.0.0.0', port))
      server_socket.listen(5)
      print(f"Server started and listening on port {port}")
  
      while True:
          client_socket, addr = server_socket.accept()
          print(f"Accepted connection from {addr}")
          welcome_message = "Welcome to the server!"
          client_socket.sendall(welcome_message.encode('utf-8'))
          client_socket.close()
  
      return f"Server started and listening on port {port}"