tftpClientAgent.java
=========================================
public class tftpClientAgent extends Thread {
    public tftpClientAgent(InetAddress ip, int port, short opcode, String fname, String mode) {
        this.m_ClientAddress = ip;
        this.m_ClientPort = port;
        this.m_curopcode = opcode;
        this.m_filename = fname;
        this.m_mode = mode;
    }
   
    public void run() {
        int nfail = 100;
        while (nfail-- > 0) {
            //try getFreePort 100 times
            try {
                this.m_so_tftp = new DatagramSocket(this.getFreePort());
                break;  //get a random port number
            } catch (SocketException e) {
            }
        }
       
        //ok, the UDP socket is ready, response to the client
        switch (this.m_curopcode) {
            case 1:
                //RRQ
                this.RRQ();
                break;
            case 2:
                //WRQ
                this.WRQ();
                //System.out.println("debug: tftpClientAgent.run() --> a WRQ ended ...");
                break;
        }
       
        this.m_so_tftp.close();
       
    }
    
}

    private InetAddress m_ClientAddress;    //ip of the client
    private int m_ClientPort;   //port of the client
    private DatagramSocket m_so_tftp;   //the socket object send or get message
    private short m_curopcode; //the current opcode( wrq/rrq )
    private String m_filename;
    private String m_mode;
    private final int m_MAX_nTimeOut = 5;

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郁闷，日志的字数限制啊 。。。
还得再加一页 。。。