python 错误怎么解决usage: test.py [-h] --port PORT test.py: error: argument --port is required

import socket
import sys
import argparse
host = 'localhost'
data_payload = 2048
backlog = 5
def echo_server(port):
"""A simple echo server"""
#create a TCP socket
sock = socket.socket (socket.AF_INET ,socket.SOCK_STREAM )
#enable reuse address/port
sock.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1)
#bind the socket to the port
server_address = (host,port)
print "starting up echo server on %s port %s"%server_address
sock.bind(server_address)
#listen to clients,backlog argument specifies the max no.of queued connections
sock.listen(backlog)
while True:
print "waiting to receive message from client "
client,address = sock.accept()
data = client.recv(data_playload)
if data:
print 'data : %s'%data
client.send(data)
print "sent %s bytes back to %s"%(data,address)
#end connection
client.close()
if __name__=='__main__':
parser = argparse.ArgumentParser(description = 'Socket Server Example')
parser .add_argument('--port',action="store",dest = "port",type=int,required=True)
given_args = parser.parse_args()
port = given_args.port
echo_server(port)

命令行参数怎么写，求大神们指教。。。

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