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    <p>I admittedly don't have any experience with Arduino, but I have a lot of experience with messing with Java Output/InputStreams. Take this with a grain of salt, as I have no way to actually test this on a real Arduino device, but if I were in your situation, this is what I'd do.</p> <p>I suspect your call to <code>stream.write("This is a very, very long string, which must be made even longer to demonstrate the problem".getBytes());</code> is actually buffering the entire string. When you subsequently call <code>stream.flush()</code>, all of the string data gets "written" to the Arduino device all at once. The reason I suspect this is because you're calling the <code>BufferedOutputStream</code> super constructor with a size of 500 bytes. First, I'd try reducing that to 64-bytes. However, I suspect this might not fix the problem either because <code>BufferedOutputStream</code> isn't going to know when to call <code>ping</code>.</p> <p>I think you're going to want to override both <code>write</code> and <code>flush</code>. The idea behind <code>flush</code>, according to the Java specification, is that <code>flush</code> is supposed to force any unwritten, buffered bytes to get written to the underlying stream:</p> <p><a href="http://docs.oracle.com/javase/7/docs/api/java/io/OutputStream.html#flush" rel="nofollow">http://docs.oracle.com/javase/7/docs/api/java/io/OutputStream.html#flush</a>()</p> <p>I'd also probably just extend plain-ole <code>OutputStream</code> and do any buffering on my own. I would override the <code>write</code> method to buffer up to 64-bytes of data at a time. If 64-bytes isn't enough space, call <code>super.write()</code> on your filled 64-byte buffer, then call <code>super.flush()</code> and then <code>ping()</code>, prior to buffering/writing any more data. Repeat this process in a while loop until your buffer has enough space to hold whatever's left of your input data. Then override <code>flush</code> to write any data that didn't completely fill your underlying 64-byte buffer (and thus did not actually get written by previous calls to <code>super.write()</code>).</p> <p>This way, if you call <code>write</code> on too much data, your class will write to the underlying stream until at most 64-bytes remain, and your subsequent call to <code>flush</code> will ensure those last few bytes actually get written to the Arduino. At the end of the day, you also get a fully-Java-compliant <code>OutputStream</code> implementation, which is nice too.</p> <p><em><strong>Edit</em></strong></p> <p>I'm using 64-bytes simply because you stated that your Arduino can handle up to that many at a time. Of course, this can be reduced if necessary, I'm just using "64" for convenience.</p>
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    1. POCreating an OutputStream with limited throughput
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    1. CO"then ping(), prior to buffering/writing any more data" - thing is, `ping()` is intended to be called from the Arduino side (when receiving a signal on the `InputStream` from Arduino). The idea is that the Arduino is sending a `ping()` when it is ready to receive more bytes.
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    2. COI see - your `write` method would need to block until it had received a ping from the Arduino. I should have been more clear. I was assuming that somehow, your Arduino would trigger a call to `ping()` when it was ready to receive more data. In that case, your overridden `write()` method would block until `ping()` got called, and `ping()` wouldn't need to do anything other than release the `write` method so that it could continue writing data.
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    3. CONah, that's not quite what I want. I want every call to `write()` to buffer up bytes, and return immediately. No blocking here. Every time `flush()` is called, 64 (or less) bytes from the buffer is written to the underlying stream. A `ping()` would cause the 64 next bytes (or less) to be written. OK, maybe I´m not strictly conforming to the specification of `OutputStream.flush()`.
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