/** * Executes a command and sends the result to the specified output stream. * * @param cmd server command * @param arg argument * @param os target output stream * @return string * @throws IOException I/O exception */ protected String exec(final ServerCmd cmd, final String arg, final OutputStream os) throws IOException { final OutputStream o = os == null ? new ArrayOutput() : os; sout.write(cmd.code); send(arg); sout.flush(); final BufferInput bi = new BufferInput(sin); ClientSession.receive(bi, o); if (!ClientSession.ok(bi)) throw new BaseXException(bi.readString()); return o.toString(); }