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<img alt="Erlang logo" src="../../../../doc/erlang-logo.png"><br><small><a href="users_guide.html">User's Guide</a><br><a href="index.html">Reference Manual</a><br><a href="release_notes.html">Release Notes</a><br><a href="../pdf/cosFileTransfer-1.1.13.pdf">PDF</a><br><a href="../../../../doc/index.html">Top</a></small><p><strong>cosFileTransfer</strong><br><strong>User's Guide</strong><br><small>Version 1.1.13</small></p>
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<h1>4 Using the File Transfer Service</h1>
<h3><a name="id61189">4.1
Overview</a></h3>
<p>This chapter describes how two File Transfer Service applications interact.</p>
<h4>Components</h4>
<p>There are several ways the OMG File Transfer Service can be used.
Below one scenario is visualized: </p>
<a name="CosFileTransfer"></a>
<img alt="IMAGE MISSING" src="CosFileTransfer.gif"><br>
<em>Figure
4.1:
Figure 1: The File Transfer Service Components.</em>
<ul>
<li>
<strong>Source ORB:</strong> this is the ORB we want to transfer a file from/via and it holds
an object reference to a
<span class="bold_code"><a href="CosFileTransfer_VirtualFileSystem.html">Virtual File System (VFS)</a></span> which,
in this example, represents an FTP server.</li>
<li>
<strong>Target ORB:</strong> the goal may be, for example, to transfer a new file or append to an
existing file placed at the location that this ORB's <span class="code">VFS</span> represents.
In this scenario it is the local disk or the NFS.</li>
<li>
<strong>Transport Protocol:</strong> initially the ORB's, i.e., target and source, communicate via
normal <span class="code">CORBA</span> requests to determine whether or not they can communicate. If the
File Transfer Service's have one, or more, <span class="code">Transport Protocol</span> in common the data
will be streamed using this protocol. The cosFileTransfer application currently supports
<span class="code">TCP/IP</span> and <span class="code">SSL</span>.</li>
</ul>
<p>Which type of file system the <span class="code">VFS</span> is supposed to represent is determined
by the options given when creating it, which is also how one determine which
<span class="code">Transport Protocol</span> to use. Hence, the source and target <span class="code">VFS</span> described above
can be started by invoking, respectively, the following operations:</p>
<div class="example"><pre>
1> SVFS = cosFileTransferApp:create_VFS('FTP', [], Host, 21, [{protocol, tcp}]),
2> TVFS = cosFileTransferApp:create_VFS({'NATIVE', 'cosFileTransferNATIVE_file'},
[], OtherHost, 0, [{protocol, tcp}]),
</pre></div>
<p>Naturally can any combination of <span class="code">VFS</span>-types be used and it is also possible
to use own drivers, i.e., <span class="code">{'NATIVE', 'MyDriver'}</span>.</p>
<p>After creating necessary <span class="code">VFS's</span> we can login in and perform operations
on files and directories residing on each file system.</p>
<h4>How To Use SSL</h4>
<p>To be able to use <span class="code">SSL</span> as transport protocol a few configuration
parameters must be set. The required parameters depend on if Orber is
the target or/and the source ORB. However, the SSL_CERT_FILE variable
must be defined in both cases.</p>
<p>Setting of a CA certificate file with an option does not work due to
weaknesses in the SSLeay package. A work-around in the ssl application is
to set the OS environment variable SSL_CERT_FILE before SSL is started.
However, then the CA certificate file will be global for all connections
(both incoming and outgoing calls).</p>
<h4>Configurations when cosFileTransfer is Used as Target</h4>
<p>The following three configuration variables can be used to configure
cosFileTransfer's SSL target behavior.</p>
<ul>
<li>
<strong>ssl_server_certfile</strong> which is a path to a file containing a
chain of PEM encoded certificates for cosFileTransfer as target.</li>
<li>
<strong>ssl_server_verify</strong> which specifies type of verification:
0 = do not verify peer; 1 = verify peer, verify client once, 2 =
verify peer, verify client once, fail if no peer certificate.
The default value is 0.</li>
<li>
<strong>ssl_server_depth</strong> which specifies verification depth, i.e.
how far in a chain of certificates the verification process shall
proceed before the verification is considered successful. The
default value is 1. </li>
</ul>
<p>There also exist a number of API functions for accessing the values of
these variables:</p>
<ul>
<li>cosFileTransferApp:ssl_server_certfile/0</li>
<li>cosFileTransferApp:ssl_server_verify/0</li>
<li>cosFileTransferApp:ssl_server_depth/0</li>
</ul>
<h4>Configurations when cosFileTransfer is used as Source</h4>
<p>Below is the list of configuration variables used when cosFileTransfer
act as the source application.</p>
<ul>
<li>
<strong>ssl_client_certfile</strong> which is a path to a file containing a
chain of PEM encoded certificates used in outgoing calls.</li>
<li>
<strong>ssl_client_verify</strong> which specifies type of verification:
0 = do not verify peer; 1 = verify peer, verify client once, 2 =
verify peer, verify client once, fail if no peer certificate.
The default value is 0.</li>
<li>
<strong>ssl_client_depth</strong> which specifies verification depth, i.e.
how far in a chain of certificates the verification process shall
proceed before the verification is considered successful. The
default value is 1. </li>
</ul>
<p>There also exist a number of API functions for accessing the values of
these variables in the client processes:</p>
<ul>
<li>cosFileTransferApp:ssl_client_certfile/0</li>
<li>cosFileTransferApp:ssl_client_verify/0</li>
<li>cosFileTransferApp:ssl_client_depth/0</li>
</ul>
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