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| 55 | <H2><A NAME="SECTION00131620000000000000000"> |
| 56 | 11.16.2 Server Objects</A> |
| 57 | </H2> |
| 58 | |
| 59 | <P> |
| 60 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 61 | <td><nobr><b><tt id='l2h-3548' xml:id='l2h-3548' class="function">fileno</tt></b>(</nobr></td> |
| 62 | <td><var></var>)</td></tr></table></dt> |
| 63 | <dd> |
| 64 | Return an integer file descriptor for the socket on which the server |
| 65 | is listening. This function is most commonly passed to |
| 66 | <tt class="function">select.select()</tt>, to allow monitoring multiple servers in the |
| 67 | same process. |
| 68 | </dl> |
| 69 | |
| 70 | <P> |
| 71 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 72 | <td><nobr><b><tt id='l2h-3549' xml:id='l2h-3549' class="function">handle_request</tt></b>(</nobr></td> |
| 73 | <td><var></var>)</td></tr></table></dt> |
| 74 | <dd> |
| 75 | Process a single request. This function calls the following methods |
| 76 | in order: <tt class="method">get_request()</tt>, <tt class="method">verify_request()</tt>, and |
| 77 | <tt class="method">process_request()</tt>. If the user-provided <tt class="method">handle()</tt> |
| 78 | method of the handler class raises an exception, the server's |
| 79 | <tt class="method">handle_error()</tt> method will be called. |
| 80 | </dl> |
| 81 | |
| 82 | <P> |
| 83 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 84 | <td><nobr><b><tt id='l2h-3550' xml:id='l2h-3550' class="function">serve_forever</tt></b>(</nobr></td> |
| 85 | <td><var></var>)</td></tr></table></dt> |
| 86 | <dd> |
| 87 | Handle an infinite number of requests. This simply calls |
| 88 | <tt class="method">handle_request()</tt> inside an infinite loop. |
| 89 | </dl> |
| 90 | |
| 91 | <P> |
| 92 | <dl><dt><b><tt id='l2h-3551' xml:id='l2h-3551'>address_family</tt></b></dt> |
| 93 | <dd> |
| 94 | The family of protocols to which the server's socket belongs. |
| 95 | <tt class="constant">socket.AF_INET</tt> and <tt class="constant">socket.AF_UNIX</tt> are two |
| 96 | possible values. |
| 97 | </dd></dl> |
| 98 | |
| 99 | <P> |
| 100 | <dl><dt><b><tt id='l2h-3552' xml:id='l2h-3552'>RequestHandlerClass</tt></b></dt> |
| 101 | <dd> |
| 102 | The user-provided request handler class; an instance of this class is |
| 103 | created for each request. |
| 104 | </dd></dl> |
| 105 | |
| 106 | <P> |
| 107 | <dl><dt><b><tt id='l2h-3553' xml:id='l2h-3553'>server_address</tt></b></dt> |
| 108 | <dd> |
| 109 | The address on which the server is listening. The format of addresses |
| 110 | varies depending on the protocol family; see the documentation for the |
| 111 | socket module for details. For Internet protocols, this is a tuple |
| 112 | containing a string giving the address, and an integer port number: |
| 113 | <code>('127.0.0.1', 80)</code>, for example. |
| 114 | </dd></dl> |
| 115 | |
| 116 | <P> |
| 117 | <dl><dt><b><tt id='l2h-3554' xml:id='l2h-3554'>socket</tt></b></dt> |
| 118 | <dd> |
| 119 | The socket object on which the server will listen for incoming requests. |
| 120 | </dd></dl> |
| 121 | |
| 122 | <P> |
| 123 | The server classes support the following class variables: |
| 124 | |
| 125 | <P> |
| 126 | <dl><dt><b><tt id='l2h-3555' xml:id='l2h-3555'>allow_reuse_address</tt></b></dt> |
| 127 | <dd> |
| 128 | Whether the server will allow the reuse of an address. This defaults |
| 129 | to <tt class="constant">False</tt>, and can be set in subclasses to change the policy. |
| 130 | </dd></dl> |
| 131 | |
| 132 | <P> |
| 133 | <dl><dt><b><tt id='l2h-3556' xml:id='l2h-3556'>request_queue_size</tt></b></dt> |
| 134 | <dd> |
| 135 | The size of the request queue. If it takes a long time to process a |
| 136 | single request, any requests that arrive while the server is busy are |
| 137 | placed into a queue, up to <tt class="member">request_queue_size</tt> requests. Once |
| 138 | the queue is full, further requests from clients will get a |
| 139 | ``Connection denied'' error. The default value is usually 5, but this |
| 140 | can be overridden by subclasses. |
| 141 | </dd></dl> |
| 142 | |
| 143 | <P> |
| 144 | <dl><dt><b><tt id='l2h-3557' xml:id='l2h-3557'>socket_type</tt></b></dt> |
| 145 | <dd> |
| 146 | The type of socket used by the server; <tt class="constant">socket.SOCK_STREAM</tt> |
| 147 | and <tt class="constant">socket.SOCK_DGRAM</tt> are two possible values. |
| 148 | </dd></dl> |
| 149 | |
| 150 | <P> |
| 151 | There are various server methods that can be overridden by subclasses |
| 152 | of base server classes like <tt class="class">TCPServer</tt>; these methods aren't |
| 153 | useful to external users of the server object. |
| 154 | |
| 155 | <P> |
| 156 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 157 | <td><nobr><b><tt id='l2h-3558' xml:id='l2h-3558' class="function">finish_request</tt></b>(</nobr></td> |
| 158 | <td><var></var>)</td></tr></table></dt> |
| 159 | <dd> |
| 160 | Actually processes the request by instantiating |
| 161 | <tt class="member">RequestHandlerClass</tt> and calling its <tt class="method">handle()</tt> method. |
| 162 | </dl> |
| 163 | |
| 164 | <P> |
| 165 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 166 | <td><nobr><b><tt id='l2h-3559' xml:id='l2h-3559' class="function">get_request</tt></b>(</nobr></td> |
| 167 | <td><var></var>)</td></tr></table></dt> |
| 168 | <dd> |
| 169 | Must accept a request from the socket, and return a 2-tuple containing |
| 170 | the <em>new</em> socket object to be used to communicate with the |
| 171 | client, and the client's address. |
| 172 | </dl> |
| 173 | |
| 174 | <P> |
| 175 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 176 | <td><nobr><b><tt id='l2h-3560' xml:id='l2h-3560' class="function">handle_error</tt></b>(</nobr></td> |
| 177 | <td><var>request, client_address</var>)</td></tr></table></dt> |
| 178 | <dd> |
| 179 | This function is called if the <tt class="member">RequestHandlerClass</tt>'s |
| 180 | <tt class="method">handle()</tt> method raises an exception. The default action is |
| 181 | to print the traceback to standard output and continue handling |
| 182 | further requests. |
| 183 | </dl> |
| 184 | |
| 185 | <P> |
| 186 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 187 | <td><nobr><b><tt id='l2h-3561' xml:id='l2h-3561' class="function">process_request</tt></b>(</nobr></td> |
| 188 | <td><var>request, client_address</var>)</td></tr></table></dt> |
| 189 | <dd> |
| 190 | Calls <tt class="method">finish_request()</tt> to create an instance of the |
| 191 | <tt class="member">RequestHandlerClass</tt>. If desired, this function can create a |
| 192 | new process or thread to handle the request; the <tt class="class">ForkingMixIn</tt> |
| 193 | and <tt class="class">ThreadingMixIn</tt> classes do this. |
| 194 | </dl> |
| 195 | |
| 196 | <P> |
| 197 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 198 | <td><nobr><b><tt id='l2h-3562' xml:id='l2h-3562' class="function">server_activate</tt></b>(</nobr></td> |
| 199 | <td><var></var>)</td></tr></table></dt> |
| 200 | <dd> |
| 201 | Called by the server's constructor to activate the server. The default |
| 202 | behavior just <tt class="method">listen</tt>s to the server's socket. |
| 203 | May be overridden. |
| 204 | </dl> |
| 205 | |
| 206 | <P> |
| 207 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 208 | <td><nobr><b><tt id='l2h-3563' xml:id='l2h-3563' class="function">server_bind</tt></b>(</nobr></td> |
| 209 | <td><var></var>)</td></tr></table></dt> |
| 210 | <dd> |
| 211 | Called by the server's constructor to bind the socket to the desired |
| 212 | address. May be overridden. |
| 213 | </dl> |
| 214 | |
| 215 | <P> |
| 216 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 217 | <td><nobr><b><tt id='l2h-3564' xml:id='l2h-3564' class="function">verify_request</tt></b>(</nobr></td> |
| 218 | <td><var>request, client_address</var>)</td></tr></table></dt> |
| 219 | <dd> |
| 220 | Must return a Boolean value; if the value is <tt class="constant">True</tt>, the request will be |
| 221 | processed, and if it's <tt class="constant">False</tt>, the request will be denied. |
| 222 | This function can be overridden to implement access controls for a server. |
| 223 | The default implementation always returns <tt class="constant">True</tt>. |
| 224 | </dl> |
| 225 | |
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