Sending file using sockets (difficult)

Question

Hi, i have the following section of code
(of which i am not claiming ownership) which
implements a DCC Send command from irc.
It accomplishes this using sockets, and while
i understand how the code accomplishes what it
does, i need help with a possible modification.
Basically what i am looking to do is keep track
of the progress of the send - so that the
user can at any time see how much of the file
has been sent and how much is remaining.
If anyone has done such a thing in the past or
has a good idea as to how this should be implemented,
i would be greatful for their help.
Here is the code:
new Thread() {
            public void run() {
                try {
                    ServerSocket ss = new ServerSocket(0);
                    ss.setSoTimeout(timeout);
                    int port = ss.getLocalPort();
                    //byte[] ip = ss.getInetAddress().getAddress();
                    byte[] ip = InetAddress.getLocalHost().getAddress();
                    long ipNum = 0;
                    long multiplier = 1;
                    for (int i = 3; i >= 0; i--) {
                        int byteVal = (ip[i] + 256) % 256;
                        ipNum += byteVal*multiplier;
                        multiplier *= 256;
                    // Rename the filename so it has no whitespace in it when we send it.
                    // .... I really should do this a bit more nicely at some point ....
                    String safeFilename = file.getName().replace(' ', '_');
                    safeFilename = safeFilename.replace('\t', '_');
                    // Send the message to the user, telling them where to connect to in order to get the file.
                    sendCTCPCommand(nick, "DCC SEND " + safeFilename + " " + ipNum + " " + port + " " + file.length());
                    // The client may now connect to us and download the file.
                    Socket socket = ss.accept();
                    socket.setSoTimeout(30000);
                    // Might as well close the server socket now; it's finished with.
                    ss.close();
                    BufferedOutputStream output = new BufferedOutputStream(socket.getOutputStream());
                    BufferedInputStream input = new BufferedInputStream(socket.getInputStream());
                    BufferedInputStream finput = new BufferedInputStream(new FileInputStream(file));
                    byte[] outBuffer = new byte[bufferSize];
                    byte[] inBuffer = new byte[4];
                    int bytesRead = 0;
                    while ((bytesRead = finput.read(outBuffer, 0, outBuffer.length)) != -1) {
                        output.write(outBuffer, 0, bytesRead);
                        output.flush();
                        input.read(inBuffer, 0, inBuffer.length);
                    output.close();
                    input.close();
                    log("+++ DCC SEND Completed to " + nick + " (" + file.getPath() + ")");
                }

Answer 1

You already have the necessary code to find the number of bytes sent at any point during the transmission. You can find out the size of the file by instantiating a RandomAccessFile before you send it, and querying for the file length.
I suggest you make the file size and bytes sent volatile and conveniently accessible to another thread (best implemented here as an inner class?). Your new thread will need to monitor the file transfer at intervals to update the progress indicator. You can generate estimates of time remaining by measuring the average transmission rate, and extrapolating using the total file size. Classically this is done using an average, but you might be better just maintaining a list of fairly recent samples, allowing for the speed swings inherent in internet connections.
How you update the progress indicator from your monitor thread is up to you. I suggest exposing methods in the UI for setting the progress and time remaining, and simply update them from the monitor.
Does this help any?