等待网络服务是否可用

#coding:utf-8
__author__ = 'similarface'
import argparse
import socket
import errno
from time import time as now

DEFAULT_TIMEOUT = 120
DEFAULT_SERVER_HOST = 'localhost'
DEFAULT_SERVER_PORT = 80

class NetServiceChecker(object):
""" Wait for a network service to come online"""
def __init__(self, host, port, timeout=DEFAULT_TIMEOUT):
self.host = host
self.port = port
self.timeout = timeout
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

def end_wait(self):
self.sock.close()

def check(self):
""" Check the service """
if self.timeout:
#超时时间间隔＋加上现在的时间
end_time = now() + self.timeout

while True:
try:
if self.timeout:
#下一次的超时时间
next_timeout = end_time - now()
if next_timeout < 0:
return False
else:
print "设置soct的timeout参数 %ss" %round(next_timeout)
self.sock.settimeout(next_timeout)
#连接sock
self.sock.connect((self.host, self.port))
# handle exceptions
except socket.timeout, err:
if self.timeout:
return False
except socket.error, err:
print "Exception: %s" %err
else:
#如果soct能建立
self.end_wait()
return True

if __name__ == '__main__':
parser = argparse.ArgumentParser(description='Wait for Network Service')
parser.add_argument('--host', action="store", dest="host",  default=DEFAULT_SERVER_HOST)
parser.add_argument('--port', action="store", dest="port", type=int, default=DEFAULT_SERVER_PORT)
parser.add_argument('--timeout', action="store", dest="timeout", type=int, default=DEFAULT_TIMEOUT)
given_args = parser.parse_args()
host, port, timeout = given_args.host, given_args.port, given_args.timeout
service_checker = NetServiceChecker(host, port, timeout=timeout)
print "检测网络服务 %s:%s ..." %(host, port)
if service_checker.check():
print "服务可用!"
else:
print "服务不可用!"