用XMLRPC开服务进行server/client通信

本文讲一下如何用python的xmlrpc开服务，进行server/client的通信。

应用场景：1）需多client访问应用程序给予应答情况——网页服务；  2）数据极大，希望加载一次，后面只用方法调用

解决方案：  开两个服务，一个数据服务，一个网络服务；
 数据服务端加载数据，网络服务端调用数据，并将结果显示在网络服务中；
 外部调用网络服务返回结果；

应用工具：xmlrpc，本文中以python 2.7.3的xmlrpclib为例，其他语言也有相应接口

下面分别说明。

1. 数据端

在本地localhost的8000端口开server服务，load数据，并定义接口查找数据第i个元素（findai）.

Server :

from SimpleXMLRPCServer import SimpleXMLRPCServerglobal adef load():global aa = [1 ,2, 24]return adef findai(i):global aprint a[i]return a[i]server = SimpleXMLRPCServer(("localhost", 8000))server.register_function(findai,"findai")load()server.serve_forever() 

Client:

import xmlrpclibproxy = xmlrpclib.ServerProxy("http://localhost:8000/")candidate = proxy.findai(1)print "the %d-th number of a is %d" %(1, candidate)

2. 数据端 + 网络端

Client:

import xmlrpclibproxy = xmlrpclib.ServerProxy("http://localhost:8000/")candidate = proxy.findai(1)print "the %d-th number of a is %d" %(1, candidate)from bottle import route, run, template@route('/hello/<name>')def index(name):return template('<b> hello {{name}} </b>', name=candidate)run(host="localhost", port=8086)

注意事项：

1. 通信数据类型

注意通讯数据类型只能是python的built-in类型（而不能是numpy类型），所以其他类型应转换为str类型（client端用ast.literal_eval从str转回来）或者更方便的用list（直接server端tolist转，client端numpy.array解）；

否则会报错：

xmlrpclib.Fault:  <Fault  8002:  "Can't serialize output: cannot marshal <type 'numpy.float64'> objects">

以string为例（其实tolist更简单），

Server:

from SimpleXMLRPCServer import SimpleXMLRPCServerglobal aimport astfrom cStringIO import StringIOfrom numpy.lib import formatimport numpyclass T:def to_string(self,arr):f = StringIO()if type(arr)==numpy.ndarray:format.write_array(f,arr)s = f.getvalue()elif isinstance(arr,str)==False:s = str(arr)return sdef from_string(self,s):if s[0]!="[": # converted from numpy arrayf = StringIO(s)arr = format.read_array(f)else:arr = ast.literal_eval(s)return arrdef load(self):global aa = [1 ,2, 24]return adef ret_a(self):global areturn aserver = SimpleXMLRPCServer(("localhost", 8002))server.register_instance(T())srv = T()srv.load()server.serve_forever() 

Client:

import xmlrpclibproxy = xmlrpclib.ServerProxy("http://localhost:8002/")candidate = proxy.ret_a()print "the variable 'a' in server is "+ str((proxy.from_string(candidate)))

2. 通讯字符编码问题

注意通讯字符必须是unicode编码，用中文的时候要小心。

所以中文的case下，在server段执行：

def gbk_to_unicode(s):    return s.decode('gbk').encode('utf-8').decode('latin1')

client端执行：

def unicode_to_gbk(s):    return s.encode('latin1').decode('utf-8').encode('gbk')

for example,

Server:

from SimpleXMLRPCServer import SimpleXMLRPCServerglobal aimport astfrom cStringIO import StringIOfrom numpy.lib import formatimport numpyimport sysdef gbk_to_unicode(s):        return s.decode('gbk').encode('utf-8').decode('latin1')class T:    def load(self): # load a dictionary with gbk elements        global a        a = {"1,1":["小","苹果"],"1,2":[1,2]}    def printf(self,s): # receive unicode, return unicode        print "received string : "+ s #unicode        return s    def idx(self,s): # transfer gbk -> unicode to client        global a        return [gbk_to_unicode(x) for x in a.get(s,[])]reload(sys)sys.setdefaultencoding('gbk')server = SimpleXMLRPCServer(("localhost", 8002))server.register_instance(T())srv = T()srv.load()server.serve_forever()

Client:

import xmlrpclibproxy = xmlrpclib.ServerProxy("http://localhost:8002/")# method 1. 用unicode编码s = u"美女"print "the variable to transfer is "+ sres_u1 = proxy.printf(s)# method 2. decode to unicodes = "美女"print "the variable to transfer is "+ sres_u2 = proxy.printf(s.decode('latin1'))assert res_u1 == res_u2res_gbk = res_u1.encode('latin1')print res_gbk# 再进一步def unicode_to_gbk(s):return s.encode('latin1').decode('utf-8').encode('gbk')res = proxy.idx("1,1") # receive unicodea =  [unicode_to_gbk(s) for s in res] # transfer unicode->gbkprint a[0], a[1]