Which of the operations causes the exception?

This may be unrelated, but your read loop has a number of serious
problems.

First, the call to available() doesn't serve any useful purpose and in
fact can give you problems on a slow network. Simply read from the
input stream until you reach EOF.

Second, don't expect read() to always read the amount you've
requested. Instead, check the return value and write only the same
number of bytes.

Also, you should be using a plain InputStream to read from the remote
and a plain OutputStream to write the file. Other stream types perform
various types of data conversion that can corrupt the contents of most
files.

/gordon