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50 lines
1.6 KiB
Java
50 lines
1.6 KiB
Java
4 years ago
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// UDPMedium.java (C) I. A. Robin, K. J. Turner 01/03/01
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package protocol;
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import java.util.*;
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import support.*;
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public class UDPMedium extends Medium {
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public UDPMedium() {
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super();
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}
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// identify and return PDU currently on channel with
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// type and parameters matching those described in given string
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// parameters are: (source port, destination port, SDU)
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protected PDU getMatchingPDU(String s) {
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UDPMessage ud;
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int sp = -1;
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int dp = -1;
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String sdu = "";
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// extract name of source entity for this datagram:
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int sourceStart = s.indexOf('[') + 1;
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int sourceEnd = s.indexOf( ']' );
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String sourceName = s.substring(sourceStart, sourceEnd);
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// get type and parameters of PDU from action string
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// PDU type starts after first space following "Deliver" or "Lose":
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int typeStart = s.indexOf(' ') + 1;
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int typeEnd = s.indexOf( '(' );
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String type = s.substring(typeStart, typeEnd);
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String[] params = getParams(s);
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sp = Integer.parseInt(params[0]); // source port
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dp = Integer.parseInt(params[1]); // destination port
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sdu = params[2];
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// try to match PDU type and seq with a PDU currently on channel:
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for (Enumeration e = pdus.elements(); e.hasMoreElements(); ) {
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ud = (UDPMessage)e.nextElement();
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if (ud != null && ud.type.equals(type)
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&& ud.getSource().getName().equals(sourceName)
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&& sp == ud.sourcePort && dp == ud.destPort
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&& sdu.equals(ud.getSDU())) {
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return ud;
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}
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}
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return null; // no match found
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}
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}
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