doc/core/howto/tutorial/client.html

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   3 <title>Twisted Documentation: The Evolution of Finger: a Twisted finger client</title>
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   8     <h1 class="title">The Evolution of Finger: a Twisted finger client</h1>
   9     <div class="toc"><ol><li><a href="#auto0">Introduction</a></li><li><a href="#auto1">Finger Proxy</a></li></ol></div>
  10     <div class="content">
  11
  12 <span/>
  13
  14 <h2>Introduction<a name="auto0"/></h2>
  15
  16 <p> This is the ninth part of the Twisted tutorial <a href="index.html" shape="rect">Twisted from Scratch, or The Evolution of Finger</a>.</p>
  17
  18 <p>In this part, we develop a client for the finger server: a proxy finger
  19 server which forwards requests to another finger server.</p>
  20
  21 <h2>Finger Proxy<a name="auto1"/></h2>
  22
  23 <p>Writing new clients with Twisted is much like writing new servers.
  24 We implement the protocol, which just gathers up all the data, and
  25 give it to the factory. The factory keeps a deferred which is triggered
  26 if the connection either fails or succeeds. When we use the client,
  27 we first make sure the deferred will never fail, by producing a message
  28 in that case. Implementing a wrapper around client which just returns
  29 the deferred is a common pattern.  While less flexible than
  30 using the factory directly, it's also more convenient.</p>
  31
  32
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 142 110
 143 </p><span class="py-src-comment"># finger proxy</span>
 144 <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">application</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">internet</span>, <span class="py-src-variable">service</span>
 145 <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">internet</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">defer</span>, <span class="py-src-variable">protocol</span>, <span class="py-src-variable">reactor</span>
 146 <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">protocols</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">basic</span>
 147 <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">python</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">components</span>
 148 <span class="py-src-keyword">from</span> <span class="py-src-variable">zope</span>.<span class="py-src-variable">interface</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">Interface</span>, <span class="py-src-variable">implements</span>
 149
 150
 151 <span class="py-src-keyword">def</span> <span class="py-src-identifier">catchError</span>(<span class="py-src-parameter">err</span>):
 152     <span class="py-src-keyword">return</span> <span class="py-src-string">&quot;Internal error in server&quot;</span>
 153
 154 <span class="py-src-keyword">class</span> <span class="py-src-identifier">IFingerService</span>(<span class="py-src-parameter">Interface</span>):
 155
 156     <span class="py-src-keyword">def</span> <span class="py-src-identifier">getUser</span>(<span class="py-src-parameter">user</span>):
 157         <span class="py-src-string">&quot;&quot;&quot;Return a deferred returning a string&quot;&quot;&quot;</span>
 158
 159     <span class="py-src-keyword">def</span> <span class="py-src-identifier">getUsers</span>():
 160         <span class="py-src-string">&quot;&quot;&quot;Return a deferred returning a list of strings&quot;&quot;&quot;</span>
 161
 162
 163 <span class="py-src-keyword">class</span> <span class="py-src-identifier">IFingerFactory</span>(<span class="py-src-parameter">Interface</span>):
 164
 165     <span class="py-src-keyword">def</span> <span class="py-src-identifier">getUser</span>(<span class="py-src-parameter">user</span>):
 166         <span class="py-src-string">&quot;&quot;&quot;Return a deferred returning a string&quot;&quot;&quot;</span>
 167
 168     <span class="py-src-keyword">def</span> <span class="py-src-identifier">buildProtocol</span>(<span class="py-src-parameter">addr</span>):
 169         <span class="py-src-string">&quot;&quot;&quot;Return a protocol returning a string&quot;&quot;&quot;</span>
 170
 171 <span class="py-src-keyword">class</span> <span class="py-src-identifier">FingerProtocol</span>(<span class="py-src-parameter">basic</span>.<span class="py-src-parameter">LineReceiver</span>):
 172
 173     <span class="py-src-keyword">def</span> <span class="py-src-identifier">lineReceived</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">user</span>):
 174         <span class="py-src-variable">d</span> = <span class="py-src-variable">self</span>.<span class="py-src-variable">factory</span>.<span class="py-src-variable">getUser</span>(<span class="py-src-variable">user</span>)
 175         <span class="py-src-variable">d</span>.<span class="py-src-variable">addErrback</span>(<span class="py-src-variable">catchError</span>)
 176         <span class="py-src-keyword">def</span> <span class="py-src-identifier">writeValue</span>(<span class="py-src-parameter">value</span>):
 177             <span class="py-src-variable">self</span>.<span class="py-src-variable">transport</span>.<span class="py-src-variable">write</span>(<span class="py-src-variable">value</span>)
 178             <span class="py-src-variable">self</span>.<span class="py-src-variable">transport</span>.<span class="py-src-variable">loseConnection</span>()
 179         <span class="py-src-variable">d</span>.<span class="py-src-variable">addCallback</span>(<span class="py-src-variable">writeValue</span>)
 180
 181
 182
 183 <span class="py-src-keyword">class</span> <span class="py-src-identifier">FingerFactoryFromService</span>(<span class="py-src-parameter">protocol</span>.<span class="py-src-parameter">ClientFactory</span>):
 184
 185     <span class="py-src-variable">implements</span>(<span class="py-src-variable">IFingerFactory</span>)
 186
 187     <span class="py-src-variable">protocol</span> = <span class="py-src-variable">FingerProtocol</span>
 188
 189     <span class="py-src-keyword">def</span> <span class="py-src-identifier">__init__</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">service</span>):
 190         <span class="py-src-variable">self</span>.<span class="py-src-variable">service</span> = <span class="py-src-variable">service</span>
 191
 192     <span class="py-src-keyword">def</span> <span class="py-src-identifier">getUser</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">user</span>):
 193         <span class="py-src-keyword">return</span> <span class="py-src-variable">self</span>.<span class="py-src-variable">service</span>.<span class="py-src-variable">getUser</span>(<span class="py-src-variable">user</span>)
 194
 195
 196 <span class="py-src-variable">components</span>.<span class="py-src-variable">registerAdapter</span>(<span class="py-src-variable">FingerFactoryFromService</span>,
 197                            <span class="py-src-variable">IFingerService</span>,
 198                            <span class="py-src-variable">IFingerFactory</span>)
 199
 200 <span class="py-src-keyword">class</span> <span class="py-src-identifier">FingerClient</span>(<span class="py-src-parameter">protocol</span>.<span class="py-src-parameter">Protocol</span>):
 201
 202     <span class="py-src-keyword">def</span> <span class="py-src-identifier">connectionMade</span>(<span class="py-src-parameter">self</span>):
 203         <span class="py-src-variable">self</span>.<span class="py-src-variable">transport</span>.<span class="py-src-variable">write</span>(<span class="py-src-variable">self</span>.<span class="py-src-variable">factory</span>.<span class="py-src-variable">user</span>+<span class="py-src-string">&quot;\r\n&quot;</span>)
 204         <span class="py-src-variable">self</span>.<span class="py-src-variable">buf</span> = []
 205
 206     <span class="py-src-keyword">def</span> <span class="py-src-identifier">dataReceived</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">data</span>):
 207         <span class="py-src-variable">self</span>.<span class="py-src-variable">buf</span>.<span class="py-src-variable">append</span>(<span class="py-src-variable">data</span>)
 208
 209     <span class="py-src-keyword">def</span> <span class="py-src-identifier">connectionLost</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">reason</span>):
 210         <span class="py-src-variable">self</span>.<span class="py-src-variable">factory</span>.<span class="py-src-variable">gotData</span>(<span class="py-src-string">''</span>.<span class="py-src-variable">join</span>(<span class="py-src-variable">self</span>.<span class="py-src-variable">buf</span>))
 211
 212 <span class="py-src-keyword">class</span> <span class="py-src-identifier">FingerClientFactory</span>(<span class="py-src-parameter">protocol</span>.<span class="py-src-parameter">ClientFactory</span>):
 213
 214     <span class="py-src-variable">protocol</span> = <span class="py-src-variable">FingerClient</span>
 215
 216     <span class="py-src-keyword">def</span> <span class="py-src-identifier">__init__</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">user</span>):
 217         <span class="py-src-variable">self</span>.<span class="py-src-variable">user</span> = <span class="py-src-variable">user</span>
 218         <span class="py-src-variable">self</span>.<span class="py-src-variable">d</span> = <span class="py-src-variable">defer</span>.<span class="py-src-variable">Deferred</span>()
 219
 220     <span class="py-src-keyword">def</span> <span class="py-src-identifier">clientConnectionFailed</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">_</span>, <span class="py-src-parameter">reason</span>):
 221         <span class="py-src-variable">self</span>.<span class="py-src-variable">d</span>.<span class="py-src-variable">errback</span>(<span class="py-src-variable">reason</span>)
 222
 223     <span class="py-src-keyword">def</span> <span class="py-src-identifier">gotData</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">data</span>):
 224         <span class="py-src-variable">self</span>.<span class="py-src-variable">d</span>.<span class="py-src-variable">callback</span>(<span class="py-src-variable">data</span>)
 225
 226
 227 <span class="py-src-keyword">def</span> <span class="py-src-identifier">finger</span>(<span class="py-src-parameter">user</span>, <span class="py-src-parameter">host</span>, <span class="py-src-parameter">port</span>=<span class="py-src-number">79</span>):
 228     <span class="py-src-variable">f</span> = <span class="py-src-variable">FingerClientFactory</span>(<span class="py-src-variable">user</span>)
 229     <span class="py-src-variable">reactor</span>.<span class="py-src-variable">connectTCP</span>(<span class="py-src-variable">host</span>, <span class="py-src-variable">port</span>, <span class="py-src-variable">f</span>)
 230     <span class="py-src-keyword">return</span> <span class="py-src-variable">f</span>.<span class="py-src-variable">d</span>
 231
 232
 233 <span class="py-src-keyword">class</span> <span class="py-src-identifier">ProxyFingerService</span>(<span class="py-src-parameter">service</span>.<span class="py-src-parameter">Service</span>):
 234     <span class="py-src-variable">implements</span>(<span class="py-src-variable">IFingerService</span>)
 235
 236     <span class="py-src-keyword">def</span> <span class="py-src-identifier">getUser</span>(<span class="py-src-parameter">self</span>, <span class="py-src-parameter">user</span>):
 237         <span class="py-src-keyword">try</span>:
 238             <span class="py-src-variable">user</span>, <span class="py-src-variable">host</span> = <span class="py-src-variable">user</span>.<span class="py-src-variable">split</span>(<span class="py-src-string">'@'</span>, <span class="py-src-number">1</span>)
 239         <span class="py-src-keyword">except</span>:
 240             <span class="py-src-variable">user</span> = <span class="py-src-variable">user</span>.<span class="py-src-variable">strip</span>()
 241             <span class="py-src-variable">host</span> = <span class="py-src-string">'127.0.0.1'</span>
 242         <span class="py-src-variable">ret</span> = <span class="py-src-variable">finger</span>(<span class="py-src-variable">user</span>, <span class="py-src-variable">host</span>)
 243         <span class="py-src-variable">ret</span>.<span class="py-src-variable">addErrback</span>(<span class="py-src-keyword">lambda</span> <span class="py-src-variable">_</span>: <span class="py-src-string">&quot;Could not connect to remote host&quot;</span>)
 244         <span class="py-src-keyword">return</span> <span class="py-src-variable">ret</span>
 245
 246     <span class="py-src-keyword">def</span> <span class="py-src-identifier">getUsers</span>(<span class="py-src-parameter">self</span>):
 247         <span class="py-src-keyword">return</span> <span class="py-src-variable">defer</span>.<span class="py-src-variable">succeed</span>([])
 248
 249 <span class="py-src-variable">application</span> = <span class="py-src-variable">service</span>.<span class="py-src-variable">Application</span>(<span class="py-src-string">'finger'</span>, <span class="py-src-variable">uid</span>=<span class="py-src-number">1</span>, <span class="py-src-variable">gid</span>=<span class="py-src-number">1</span>)
 250 <span class="py-src-variable">f</span> = <span class="py-src-variable">ProxyFingerService</span>()
 251 <span class="py-src-variable">internet</span>.<span class="py-src-variable">TCPServer</span>(<span class="py-src-number">7779</span>, <span class="py-src-variable">IFingerFactory</span>(<span class="py-src-variable">f</span>)).<span class="py-src-variable">setServiceParent</span>(
 252     <span class="py-src-variable">service</span>.<span class="py-src-variable">IServiceCollection</span>(<span class="py-src-variable">application</span>))
 253 </pre><div class="caption">Source listing - <a href="listings/finger/fingerproxy.tac"><span class="filename">listings/finger/fingerproxy.tac</span></a></div></div>
 254
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