If you set a timeout on the control connection and then make a data transfer (upload, download) which takes longer than that timeout, the client throws the following exception. It seems like the client tries to read something from the control connection while the data transfer is in progress and then it just throws an exception. It makes the application think that the transfer failed even though it succeeded.
aused by: java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read(BufferedInputStream.java:235)
at java.io.FilterInputStream.read(FilterInputStream.java:66)
at java.io.PushbackInputStream.read(PushbackInputStream.java:120)
at org.apache.commons.net.io.FromNetASCIIInputStream.__read(FromNetASCIIInputStream.java:75)
at org.apache.commons.net.io.FromNetASCIIInputStream.read(FromNetASCIIInputStream.java:170)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read(BufferedInputStream.java:235)
at org.apache.commons.net.telnet.TelnetInputStream.__read(TelnetInputStream.java:114)
at org.apache.commons.net.telnet.TelnetInputStream.run(TelnetInputStream.java:535)
at java.lang.Thread.run(Thread.java:595)
). 
Bug
Closed
Major
wrong handling of timeouts
. I could not attach the complete test since I use another layer on top of commons-net and I am not free to distribute it.
public class DelayedByteArrayInputStream extends InputStream {
private byte[] data;
private int position;
private long chunkDelay;
private final static int CHUNK = 10000;
public DelayedByteArrayInputStream(byte[] data, long time) {
this.data = data;
position = 0;
double x = time / (data.length / CHUNK);
chunkDelay = Math.round(Math.ceil(x));
}
public int read() throws IOException {
if (position % CHUNK == 0) {
try {
Thread.sleep(chunkDelay);
}
catch (InterruptedException e) {
throw new IOException("sleep interrupted");
}
}
return position < data.length ? data
public class DelayedByteArrayInputStream extends InputStream {
private byte[] data;
private int position;
private long chunkDelay;
private final static int CHUNK = 10000;
public DelayedByteArrayInputStream(byte[] data, long time) { this.data = data; position = 0; double x = time / (data.length / CHUNK); chunkDelay = Math.round(Math.ceil(x)); }
public int read() throws IOException {
if (position % CHUNK == 0) {
try { Thread.sleep(chunkDelay); }
catch (InterruptedException e) { throw new IOException("sleep interrupted"); }
}
return position < data.length ? data[position++] : -1;
}
}