 Notice that, if
<tt>i</tt> is 1 or absent, this is effectively the total
number of bytes sent.  In case of error, the method returns
<b><tt>nil</tt></b>, followed by an error message, followed
by the index of the last byte within <tt>[i, j]</tt> that
has been sent. You might want to try again from the byte
following that.  The error message can be '<tt>closed</tt>'
in case the connection was  closed before the transmission
was  completed or the string  '<tt>timeout</tt>'  in  case
there was  a  timeout  du