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|  | <title>mod_proxy_ajp - Apache HTTP Server</title> | 
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|  | <p class="apache">Apache HTTP Server Version 2.3</p> | 
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|  | <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a> > <a href="./">Modules</a></div> | 
|  | <div id="page-content"> | 
|  | <div id="preamble"><h1>Apache Module mod_proxy_ajp</h1> | 
|  | <div class="toplang"> | 
|  | <p><span>Available Languages: </span><a href="../en/mod/mod_proxy_ajp.html" title="English"> en </a> | | 
|  | <a href="../ja/mod/mod_proxy_ajp.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p> | 
|  | </div> | 
|  | <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>AJP support module for | 
|  | <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></td></tr> | 
|  | <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr> | 
|  | <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>proxy_ajp_module</td></tr> | 
|  | <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>proxy_ajp.c</td></tr> | 
|  | <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.1 and later</td></tr></table> | 
|  | <h3>Summary</h3> | 
|  |  | 
|  | <p>This module <em>requires</em> the service of <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>. It provides support for the | 
|  | <code>Apache JServ Protocol version 1.3</code> (hereafter | 
|  | <em>AJP13</em>).</p> | 
|  |  | 
|  | <p>Thus, in order to get the ability of handling <code>AJP13</code> | 
|  | protocol, <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> and | 
|  | <code class="module"><a href="../mod/mod_proxy_ajp.html">mod_proxy_ajp</a></code> have to be present in the server.</p> | 
|  |  | 
|  | <div class="warning"><h3>Warning</h3> | 
|  | <p>Do not enable proxying until you have <a href="mod_proxy.html#access">secured your server</a>. Open proxy | 
|  | servers are dangerous both to your network and to the Internet at | 
|  | large.</p> | 
|  | </div> | 
|  | </div> | 
|  | <div id="quickview"><h3 class="directives">Directives</h3> | 
|  | <p>This module provides no | 
|  | directives.</p> | 
|  | <h3>Topics</h3> | 
|  | <ul id="topics"> | 
|  | <li><img alt="" src="../images/down.gif" /> <a href="#overviewprotocol">Overview of the protocol</a></li> | 
|  | <li><img alt="" src="../images/down.gif" /> <a href="#basppacketstruct">Basic Packet Structure</a></li> | 
|  | <li><img alt="" src="../images/down.gif" /> <a href="#rpacetstruct">Request Packet Structure</a></li> | 
|  | <li><img alt="" src="../images/down.gif" /> <a href="#resppacketstruct">Response Packet Structure</a></li> | 
|  | </ul><h3>See also</h3> | 
|  | <ul class="seealso"> | 
|  | <li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></li> | 
|  | </ul></div> | 
|  | <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> | 
|  | <div class="section"> | 
|  | <h2><a name="overviewprotocol" id="overviewprotocol">Overview of the protocol</a></h2> | 
|  | <p>The <code>AJP13</code> protocol is packet-oriented.  A binary format | 
|  | was presumably chosen over the more readable plain text for reasons of | 
|  | performance.  The web server communicates with the servlet container over | 
|  | TCP connections.  To cut down on the expensive process of socket creation, | 
|  | the web server will attempt to maintain persistent TCP connections to the | 
|  | servlet container, and to reuse a connection for multiple request/response | 
|  | cycles.</p> | 
|  | <p>Once a connection is assigned to a particular request, it will not be | 
|  | used for any others until the request-handling cycle has terminated.  In | 
|  | other words, requests are not multiplexed over connections.  This makes | 
|  | for much simpler code at either end of the connection, although it does | 
|  | cause more connections to be open at once.</p> | 
|  | <p>Once the web server has opened a connection to the servlet container, | 
|  | the connection can be in one of the following states:</p> | 
|  | <ul> | 
|  | <li> Idle <br /> No request is being handled over this connection. </li> | 
|  | <li> Assigned <br /> The connecton is handling a specific request.</li> | 
|  | </ul> | 
|  | <p>Once a connection is assigned to handle a particular request, the basic | 
|  | request informaton (e.g. HTTP headers, etc) is sent over the connection in | 
|  | a highly condensed form (e.g. common strings are encoded as integers). | 
|  | Details of that format are below in Request Packet Structure. If there is a | 
|  | body to the request <code>(content-length > 0)</code>, that is sent in a | 
|  | separate packet immediately after.</p> | 
|  | <p>At this point, the servlet container is presumably ready to start | 
|  | processing the request.  As it does so, it can send the | 
|  | following messages back to the web server:</p> | 
|  | <ul> | 
|  | <li>SEND_HEADERS <br />Send a set of headers back to the browser.</li> | 
|  | <li>SEND_BODY_CHUNK <br />Send a chunk of body data back to the browser. | 
|  | </li> | 
|  | <li>GET_BODY_CHUNK <br />Get further data from the request if it hasn't all | 
|  | been transferred yet.  This is necessary because the packets have a fixed | 
|  | maximum size and arbitrary amounts of data can be included the body of a | 
|  | request (for uploaded files, for example).  (Note: this is unrelated to | 
|  | HTTP chunked tranfer).</li> | 
|  | <li>END_RESPONSE <br /> Finish the request-handling cycle.</li> | 
|  | </ul> | 
|  | <p>Each message is accompanied by a differently formatted packet of data. | 
|  | See Response Packet Structures below for details.</p> | 
|  | </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> | 
|  | <div class="section"> | 
|  | <h2><a name="basppacketstruct" id="basppacketstruct">Basic Packet Structure</a></h2> | 
|  | <p>There is a bit of an XDR heritage to this protocol, but it differs | 
|  | in lots of ways (no 4 byte alignment, for example).</p> | 
|  | <p>Byte order: I am not clear about the endian-ness of the individual | 
|  | bytes.  I'm guessing the bytes are little-endian, because that's what | 
|  | XDR specifies, and I'm guessing that sys/socket library is magically | 
|  | making that so (on the C side).  If anyone with a better knowledge of | 
|  | socket calls can step in, that would be great.</p> | 
|  | <p>There are four data types in the protocol: bytes, booleans, | 
|  | integers and strings.</p> | 
|  | <dl> | 
|  | <dt><strong>Byte</strong></dt><dd>A single byte.</dd> | 
|  | <dt><strong>Boolean</strong></dt> | 
|  | <dd>A single byte, <code>1 = true</code>, <code>0 = false</code>. | 
|  | Using other non-zero values as true (i.e. C-style) may work in some places, | 
|  | but it won't in others.</dd> | 
|  | <dt><strong>Integer</strong></dt> | 
|  | <dd>A number in the range of <code>0 to 2^16 (32768)</code>.  Stored in | 
|  | 2 bytes with the high-order byte first.</dd> | 
|  | <dt><strong>String</strong></dt> | 
|  | <dd>A variable-sized string (length bounded by 2^16). Encoded with | 
|  | the length packed into two bytes first, followed by the string | 
|  | (including the terminating '\0').  Note that the encoded length does | 
|  | <strong>not</strong> include the trailing '\0' -- it is like | 
|  | <code>strlen</code>.  This is a touch confusing on the Java side, which | 
|  | is littered with odd autoincrement statements to skip over these | 
|  | terminators.  I believe the reason this was done was to allow the C | 
|  | code to be extra efficient when reading strings which the servlet | 
|  | container is sending back -- with the terminating \0 character, the | 
|  | C code can pass around references into a single buffer, without copying. | 
|  | if the \0 was missing, the C code would have to copy things out in order | 
|  | to get its notion of a string.</dd> | 
|  | </dl> | 
|  |  | 
|  | <h3>Packet Size</h3> | 
|  | <p>According to much of the code, the max packet size is <code> | 
|  | 8 * 1024 bytes (8K)</code>.  The actual length of the packet is encoded in | 
|  | the header.</p> | 
|  |  | 
|  | <h3>Packet Headers</h3> | 
|  | <p>Packets sent from the server to the container begin with | 
|  | <code>0x1234</code>.  Packets sent from the container to the server | 
|  | begin with <code>AB</code> (that's the ASCII code for A followed by the | 
|  | ASCII code for B).  After those first two bytes, there is an integer | 
|  | (encoded as above) with the length of the payload.  Although this might | 
|  | suggest that the maximum payload could be as large as 2^16, in fact, the | 
|  | code sets the maximum to be 8K.</p> | 
|  | <table> | 
|  | <tr> | 
|  | <td colspan="6"><em>Packet Format (Server->Container)</em></td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>Byte</td> | 
|  | <td>0</td> | 
|  | <td>1</td> | 
|  | <td>2</td> | 
|  | <td>3</td> | 
|  | <td>4...(n+3)</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>Contents</td> | 
|  | <td>0x12</td> | 
|  | <td>0x34</td> | 
|  | <td colspan="2">Data Length (n)</td> | 
|  | <td>Data</td> | 
|  | </tr> | 
|  | </table> | 
|  | <table> | 
|  | <tr> | 
|  | <td colspan="6"><em>Packet Format (Container->Server)</em></td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>Byte</td> | 
|  | <td>0</td> | 
|  | <td>1</td> | 
|  | <td>2</td> | 
|  | <td>3</td> | 
|  | <td>4...(n+3)</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>Contents</td> | 
|  | <td>A</td> | 
|  | <td>B</td> | 
|  | <td colspan="2">Data Length (n)</td> | 
|  | <td>Data</td> | 
|  | </tr> | 
|  | </table> | 
|  | <p>For most packets, the first byte of the payload encodes the type of | 
|  | message.  The exception is for request body packets sent from the server to | 
|  | the container -- they are sent with a standard packet header (<code> | 
|  | 0x1234</code> and then length of the packet), but without any prefix code | 
|  | after that.</p> | 
|  | <p>The web server can send the following messages to the servlet | 
|  | container:</p> | 
|  | <table> | 
|  | <tr> | 
|  | <td>Code</td> | 
|  | <td>Type of Packet</td> | 
|  | <td>Meaning</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>2</td> | 
|  | <td>Forward Request</td> | 
|  | <td>Begin the request-processing cycle with the following data</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>7</td> | 
|  | <td>Shutdown</td> | 
|  | <td>The web server asks the container to shut itself down.</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>8</td> | 
|  | <td>Ping</td> | 
|  | <td>The web server asks the container to take control | 
|  | (secure login phase).</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>10</td> | 
|  | <td>CPing</td> | 
|  | <td>The web server asks the container to respond quickly with a CPong. | 
|  | </td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>none</td> | 
|  | <td>Data</td> | 
|  | <td>Size (2 bytes) and corresponding body data.</td> | 
|  | </tr> | 
|  | </table> | 
|  | <p>To ensure some basic security, the container will only actually do the | 
|  | <code>Shutdown</code> if the request comes from the same machine on which | 
|  | it's hosted.</p> | 
|  | <p>The first <code>Data</code> packet is send immediatly after the | 
|  | <code>Forward Request</code> by the web server.</p> | 
|  | <p>The servlet container can send the following types of messages to the | 
|  | webserver:</p> | 
|  | <table> | 
|  | <tr> | 
|  | <td>Code</td> | 
|  | <td>Type of Packet</td> | 
|  | <td>Meaning</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>3</td> | 
|  | <td>Send Body Chunk</td> | 
|  | <td>Send a chunk of the body from the servlet container to the web | 
|  | server (and presumably, onto the browser). </td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>4</td> | 
|  | <td>Send Headers</td> | 
|  | <td>Send the response headers from the servlet container to the web | 
|  | server (and presumably, onto the browser).</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>5</td> | 
|  | <td>End Response</td> | 
|  | <td>Marks the end of the response (and thus the request-handling cycle). | 
|  | </td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>6</td> | 
|  | <td>Get Body Chunk</td> | 
|  | <td>Get further data from the request if it hasn't all been | 
|  | transferred yet.</td> | 
|  | </tr> | 
|  | <tr> | 
|  | <td>9</td> | 
|  | <td>CPong Reply</td> | 
|  | <td>The reply to a CPing request</td> | 
|  | </tr> | 
|  | </table> | 
|  | <p>Each of the above messages has a different internal structure, detailed | 
|  | below.</p> | 
|  |  | 
|  | </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> | 
|  | <div class="section"> | 
|  | <h2><a name="rpacetstruct" id="rpacetstruct">Request Packet Structure</a></h2> | 
|  | <p>For messages from the server to the container of type | 
|  | <em>Forward Request</em>:</p> | 
|  | <div class="example"><pre> | 
|  | AJP13_FORWARD_REQUEST := | 
|  | prefix_code      (byte) 0x02 = JK_AJP13_FORWARD_REQUEST | 
|  | method           (byte) | 
|  | protocol         (string) | 
|  | req_uri          (string) | 
|  | remote_addr      (string) | 
|  | remote_host      (string) | 
|  | server_name      (string) | 
|  | server_port      (integer) | 
|  | is_ssl           (boolean) | 
|  | num_headers      (integer) | 
|  | request_headers *(req_header_name req_header_value) | 
|  | attributes      *(attribut_name attribute_value) | 
|  | request_terminator (byte) OxFF | 
|  | </pre></div> | 
|  | <p>The <code>request_headers</code> have the following structure: | 
|  | </p><div class="example"><pre> | 
|  | req_header_name := | 
|  | sc_req_header_name | (string)  [see below for how this is parsed] | 
|  |  | 
|  | sc_req_header_name := 0xA0xx (integer) | 
|  |  | 
|  | req_header_value := (string) | 
|  | </pre></div> | 
|  | <p>The <code>attributes</code> are optional and have the following | 
|  | structure:</p> | 
|  | <div class="example"><pre> | 
|  | attribute_name := sc_a_name | (sc_a_req_attribute string) | 
|  |  | 
|  | attribute_value := (string) | 
|  |  | 
|  | </pre></div> | 
|  | <p>Not that the all-important header is <code>content-length</code>, | 
|  | because it determines whether or not the container looks for another | 
|  | packet immediately.</p> | 
|  | <h3>Detailed description of the elements of Forward Request | 
|  | </h3> | 
|  | <h3>Request prefix</h3> | 
|  | <p>For all requests, this will be 2. See above for details on other Prefix | 
|  | codes.</p> | 
|  |  | 
|  | <h3>Method</h3> | 
|  | <p>The HTTP method, encoded as a single byte:</p> | 
|  | <table> | 
|  | <tr><td>Command Name</td><td>Code</td></tr> | 
|  | <tr><td>OPTIONS</td><td>1</td></tr> | 
|  | <tr><td>GET</td><td>2</td></tr> | 
|  | <tr><td>HEAD</td><td>3</td></tr> | 
|  | <tr><td>POST</td><td>4</td></tr> | 
|  | <tr><td>PUT</td><td>5</td></tr> | 
|  | <tr><td>DELETE</td><td>6</td></tr> | 
|  | <tr><td>TRACE</td><td>7</td></tr> | 
|  | <tr><td>PROPFIND</td><td>8</td></tr> | 
|  | <tr><td>PROPPATCH</td><td>9</td></tr> | 
|  | <tr><td>MKCOL</td><td>10</td></tr> | 
|  | <tr><td>COPY</td><td>11</td></tr> | 
|  | <tr><td>MOVE</td><td>12</td></tr> | 
|  | <tr><td>LOCK</td><td>13</td></tr> | 
|  | <tr><td>UNLOCK</td><td>14</td></tr> | 
|  | <tr><td>ACL</td><td>15</td></tr> | 
|  | <tr><td>REPORT</td><td>16</td></tr> | 
|  | <tr><td>VERSION-CONTROL</td><td>17</td></tr> | 
|  | <tr><td>CHECKIN</td><td>18</td></tr> | 
|  | <tr><td>CHECKOUT</td><td>19</td></tr> | 
|  | <tr><td>UNCHECKOUT</td><td>20</td></tr> | 
|  | <tr><td>SEARCH</td><td>21</td></tr> | 
|  | <tr><td>MKWORKSPACE</td><td>22</td></tr> | 
|  | <tr><td>UPDATE</td><td>23</td></tr> | 
|  | <tr><td>LABEL</td><td>24</td></tr> | 
|  | <tr><td>MERGE</td><td>25</td></tr> | 
|  | <tr><td>BASELINE_CONTROL</td><td>26</td></tr> | 
|  | <tr><td>MKACTIVITY</td><td>27</td></tr> | 
|  | </table> | 
|  | <p>Later version of ajp13, will transport | 
|  | additional methods, even if they are not in this list.</p> | 
|  |  | 
|  | <h3>protocol, req_uri, remote_addr, remote_host, server_name, | 
|  | server_port, is_ssl</h3> | 
|  | <p>These are all fairly self-explanatory.  Each of these is required, and | 
|  | will be sent for every request.</p> | 
|  |  | 
|  | <h3>Headers</h3> | 
|  | <p>The structure of <code>request_headers</code> is the following: | 
|  | First, the number of headers <code>num_headers</code> is encoded. | 
|  | Then, a series of header name <code>req_header_name</code> / value | 
|  | <code>req_header_value</code> pairs follows. | 
|  | Common header names are encoded as integers, | 
|  | to save space.  If the header name is not in the list of basic headers, | 
|  | it is encoded normally (as a string, with prefixed length).  The list of | 
|  | common headers <code>sc_req_header_name</code>and their codes | 
|  | is as follows (all are case-sensitive):</p> | 
|  | <table> | 
|  | <tr><td>Name</td><td>Code value</td><td>Code name</td></tr> | 
|  | <tr><td>accept</td><td>0xA001</td><td>SC_REQ_ACCEPT</td></tr> | 
|  | <tr><td>accept-charset</td><td>0xA002</td><td>SC_REQ_ACCEPT_CHARSET | 
|  | </td></tr> | 
|  | <tr><td>accept-encoding</td><td>0xA003</td><td>SC_REQ_ACCEPT_ENCODING | 
|  | </td></tr> | 
|  | <tr><td>accept-language</td><td>0xA004</td><td>SC_REQ_ACCEPT_LANGUAGE | 
|  | </td></tr> | 
|  | <tr><td>authorization</td><td>0xA005</td><td>SC_REQ_AUTHORIZATION</td> | 
|  | </tr> | 
|  | <tr><td>connection</td><td>0xA006</td><td>SC_REQ_CONNECTION</td></tr> | 
|  | <tr><td>content-type</td><td>0xA007</td><td>SC_REQ_CONTENT_TYPE</td> | 
|  | </tr> | 
|  | <tr><td>content-length</td><td>0xA008</td><td>SC_REQ_CONTENT_LENGTH</td> | 
|  | </tr> | 
|  | <tr><td>cookie</td><td>0xA009</td><td>SC_REQ_COOKIE</td></tr> | 
|  | <tr><td>cookie2</td><td>0xA00A</td><td>SC_REQ_COOKIE2</td></tr> | 
|  | <tr><td>host</td><td>0xA00B</td><td>SC_REQ_HOST</td></tr> | 
|  | <tr><td>pragma</td><td>0xA00C</td><td>SC_REQ_PRAGMA</td></tr> | 
|  | <tr><td>referer</td><td>0xA00D</td><td>SC_REQ_REFERER</td></tr> | 
|  | <tr><td>user-agent</td><td>0xA00E</td><td>SC_REQ_USER_AGENT</td></tr> | 
|  | </table> | 
|  | <p>The Java code that reads this grabs the first two-byte integer and if | 
|  | it sees an <code>'0xA0'</code> in the most significant | 
|  | byte, it uses the integer in the second byte as an index into an array of | 
|  | header names.  If the first byte is not <code>0xA0</code>, it assumes that | 
|  | the two-byte integer is the length of a string, which is then read in.</p> | 
|  | <p>This works on the assumption that no header names will have length | 
|  | greater than <code>0x9999 (==0xA000 - 1)</code>, which is perfectly | 
|  | reasonable, though somewhat arbitrary.</p> | 
|  | <div class="note"><h3>Note:</h3> | 
|  | The <code>content-length</code> header is extremely | 
|  | important.  If it is present and non-zero, the container assumes that | 
|  | the request has a body (a POST request, for example), and immediately | 
|  | reads a separate packet off the input stream to get that body. | 
|  | </div> | 
|  |  | 
|  | <h3>Attributes</h3> | 
|  | <p>The attributes prefixed with a <code>?</code> | 
|  | (e.g. <code>?context</code>) are all optional.  For each, there is a | 
|  | single byte code to indicate the type of attribute, and then its value | 
|  | (string or integer).  They can be sent in any order (though the C code | 
|  | always sends them in the order listed below).  A special terminating code | 
|  | is sent to signal the end of the list of optional attributes. The list of | 
|  | byte codes is:</p> | 
|  | <table> | 
|  | <tr><td>Information</td><td>Code Value</td><td>Type Of Value</td><td>Note</td></tr> | 
|  | <tr><td>?context</td><td>0x01</td><td>-</td><td>Not currently implemented | 
|  | </td></tr> | 
|  | <tr><td>?servlet_path</td><td>0x02</td><td>-</td><td>Not currently implemented | 
|  | </td></tr> | 
|  | <tr><td>?remote_user</td><td>0x03</td><td>String</td><td /></tr> | 
|  | <tr><td>?auth_type</td><td>0x04</td><td>String</td><td /></tr> | 
|  | <tr><td>?query_string</td><td>0x05</td><td>String</td><td /></tr> | 
|  | <tr><td>?jvm_route</td><td>0x06</td><td>String</td><td /></tr> | 
|  | <tr><td>?ssl_cert</td><td>0x07</td><td>String</td><td /></tr> | 
|  | <tr><td>?ssl_cipher</td><td>0x08</td><td>String</td><td /></tr> | 
|  | <tr><td>?ssl_session</td><td>0x09</td><td>String</td><td /></tr> | 
|  | <tr><td>?req_attribute</td><td>0x0A</td><td>String</td><td>Name (the name of the | 
|  | attribute follows)</td></tr> | 
|  | <tr><td>?ssl_key_size</td><td>0x0B</td><td>Integer</td><td /></tr> | 
|  | <tr><td>are_done</td><td>0xFF</td><td>-</td><td>request_terminator</td></tr> | 
|  | </table> | 
|  | <p>The <code>context</code> and <code>servlet_path</code> are not | 
|  | currently set by the C code, and most of the Java code completely ignores | 
|  | whatever is sent over for those fields (and some of it will actually break | 
|  | if a string is sent along after one of those codes).  I don't know if this | 
|  | is a bug or an unimplemented feature or just vestigial code, but it's | 
|  | missing from both sides of the connection.</p> | 
|  | <p>The <code>remote_user</code> and <code>auth_type</code> presumably | 
|  | refer to HTTP-level authentication, and communicate the remote user's | 
|  | username and the type of authentication used to establish their identity | 
|  | (e.g. Basic, Digest).</p> | 
|  | <p>The <code>query_string</code>, <code>ssl_cert</code>, | 
|  | <code>ssl_cipher</code>, and <code>ssl_session</code> refer to the | 
|  | corresponding pieces of HTTP and HTTPS.</p> | 
|  | <p>The <code>jvm_route</code>, is used to support sticky | 
|  | sessions -- associating a user's sesson with a particular Tomcat instance | 
|  | in the presence of multiple, load-balancing servers.</p> | 
|  | <p>Beyond this list of basic attributes, any number of other attributes | 
|  | can be sent via the <code>req_attribute</code> code <code>0x0A</code>. | 
|  | A pair of strings to represent the attribute name and value are sent | 
|  | immediately after each instance of that code.  Environment values are passed | 
|  | in via this method.</p> | 
|  | <p>Finally, after all the attributes have been sent, the attribute | 
|  | terminator, <code>0xFF</code>, is sent.  This signals both the end of the | 
|  | list of attributes and also then end of the Request Packet.</p> | 
|  |  | 
|  | </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> | 
|  | <div class="section"> | 
|  | <h2><a name="resppacketstruct" id="resppacketstruct">Response Packet Structure</a></h2> | 
|  | <p>for messages which the container can send back to the server.</p> | 
|  | <div class="example"><pre> | 
|  | AJP13_SEND_BODY_CHUNK := | 
|  | prefix_code   3 | 
|  | chunk_length  (integer) | 
|  | chunk        *(byte) | 
|  |  | 
|  |  | 
|  | AJP13_SEND_HEADERS := | 
|  | prefix_code       4 | 
|  | http_status_code  (integer) | 
|  | http_status_msg   (string) | 
|  | num_headers       (integer) | 
|  | response_headers *(res_header_name header_value) | 
|  |  | 
|  | res_header_name := | 
|  | sc_res_header_name | (string)   [see below for how this is parsed] | 
|  |  | 
|  | sc_res_header_name := 0xA0 (byte) | 
|  |  | 
|  | header_value := (string) | 
|  |  | 
|  | AJP13_END_RESPONSE := | 
|  | prefix_code       5 | 
|  | reuse             (boolean) | 
|  |  | 
|  |  | 
|  | AJP13_GET_BODY_CHUNK := | 
|  | prefix_code       6 | 
|  | requested_length  (integer) | 
|  | </pre></div> | 
|  | <h3>Details:</h3> | 
|  | <h3>Send Body Chunk</h3> | 
|  | <p>The chunk is basically binary data, and is sent directly back to the | 
|  | browser.</p> | 
|  |  | 
|  | <h3>Send Headers</h3> | 
|  | <p>The status code and message are the usual HTTP things | 
|  | (e.g. <code>200</code> and <code>OK</code>). The response header names are | 
|  | encoded the same way the request header names are. See header_encoding above | 
|  | for details about how the the codes are distinguished from the strings.<br /> | 
|  | The codes for common headers are:</p> | 
|  | <table> | 
|  | <tr><td>Name</td><td>Code value</td></tr> | 
|  | <tr><td>Content-Type</td><td>0xA001</td></tr> | 
|  | <tr><td>Content-Language</td><td>0xA002</td></tr> | 
|  | <tr><td>Content-Length</td><td>0xA003</td></tr> | 
|  | <tr><td>Date</td><td>0xA004</td></tr> | 
|  | <tr><td>Last-Modified</td><td>0xA005</td></tr> | 
|  | <tr><td>Location</td><td>0xA006</td></tr> | 
|  | <tr><td>Set-Cookie</td><td>0xA007</td></tr> | 
|  | <tr><td>Set-Cookie2</td><td>0xA008</td></tr> | 
|  | <tr><td>Servlet-Engine</td><td>0xA009</td></tr> | 
|  | <tr><td>Status</td><td>0xA00A</td></tr> | 
|  | <tr><td>WWW-Authenticate</td><td>0xA00B</td></tr> | 
|  | </table> | 
|  | <p> After the code or the string header name, the header value is | 
|  | immediately encoded.</p> | 
|  |  | 
|  | <h3>End Response</h3> | 
|  | <p>Signals the end of this request-handling cycle.  If the | 
|  | <code>reuse</code> flag is true <code>(==1)</code>, this TCP connection can | 
|  | now be used to handle new incoming requests.  If <code>reuse</code> is false | 
|  | (anything other than 1 in the actual C code), the connection should | 
|  | be closed.</p> | 
|  |  | 
|  | <h3>Get Body Chunk</h3> | 
|  | <p>The container asks for more data from the request (If the body was | 
|  | too large to fit in the first packet sent over or when the request is | 
|  | chuncked). The server will send a body packet back with an amount of data | 
|  | which is the minimum of the <code>request_length</code>, the maximum send | 
|  | body size <code>(8186 (8 Kbytes - 6))</code>, and the number of bytes | 
|  | actually left to send from the request body.<br /> | 
|  | If there is no more data in the body (i.e. the servlet container is | 
|  | trying to read past the end of the body), the server will send back an | 
|  | <em>empty</em> packet, which is a body packet with a payload length of 0. | 
|  | <code>(0x12,0x34,0x00,0x00)</code></p> | 
|  |  | 
|  | </div> | 
|  | </div> | 
|  | <div class="bottomlang"> | 
|  | <p><span>Available Languages: </span><a href="../en/mod/mod_proxy_ajp.html" title="English"> en </a> | | 
|  | <a href="../ja/mod/mod_proxy_ajp.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p> | 
|  | </div><div id="footer"> | 
|  | <p class="apache">Copyright 2006 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> | 
|  | <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div> | 
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