/dd>
<dd><code>expectedByteLen</code> - length of file, as reported by sender. 0 if 
                        not given by sender.</dd>
<dd><code>senderCallsign</code> - callsign of the sending device</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>MPReceiver instance that will handle the file receive,
         or null to indicate that this system already has the file
         and does not want to receive again.</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code>java.io.IOException<