code: public void writeFile(byte[] handle, UnsignedInteger64 offset, byte[] data,
  			int off, int len) throws SftpStatusException, SshException {
  
  		getOKRequestStatus(postWriteRequest(handle, offset.longValue(), data,
  				off, len));
  	}
docs: Write a block of data to an open file.
  
  @param handle
  the open file handle.
  @param offset
  the offset in the file to start writing
  @param data
  a buffer containing the data to write
  @param off
  the offset to start in the buffer
  @param len
  the length of data to write (setting to false will increase
  file transfer but may miss errors)
  @throws SshException