Metacat

  <p>Due to a Java limitation on the HTTP PUT comand, the data upload portion

  of Metacat deviates from the standard HTTP interface.  A standard bidirectional 

  TCP/IP socket is used for tranfering the data.  The procedure for uploading a 

  file is as follows.</p>

  <ol>

    <li>The client must login to Metacat and get a session_id</li>

    <li>The client sends a request to the servlet with an action of 'getdataport'.</li>

    <li>The server responds with an xml message that includes a port number.  The

    message looks like: <pre>&lt;xml version="1.0"?&gt;&lt;port&gt;xxxx&lt;/port&gt;</pre>

    where xxxx is an open port between 0 and 65000.</li>

    <li>The client then can create a socket connection to the returned port.

    Note that the client must make this connection within 30 seconds or the 

    port will close.</li>

    <li>The data can now be sent but first, some extra information must be

    appended onto the beginning of the data stream.  The extra information looks

    like: <pre> [filename]0[sessionID]0[filelength]0[DATA] </pre> The filename, 

    sessionID and filelength must be converted into a byte string, terminated

    with a 0 (zero) byte and inserted into the stream in the order shown.  The

    filelength is in bytes.  The DATA stream does not need to be terminated with

    a 0 byte.</li>

    <li>After the upload the server will return either an error message or

    a success message which will include the docid of the new data file.  Both

    messages are encoded in xml (like the port message). The success message

    looks like:

    <pre>&lt;?xml version="1.0"?&gt;&lt;docid&gt;yyyy&lt;/docid&gt;</pre>

    where yyyy is the new docid.</li>

  </ul>

  <p>The file DataStreamTest.java is a test class that shows how a client

  must operate to successfully upload a data file to Metacat.</p>