What is missing to get this compiled ?

["Hultman, Sten" <sten dot hultman at cgey dot com>]

This sort program compiles with no problem with gcc2.95.2 on HP-UX10.20:

#include <iostream.h>

class isockstream: public istream {
public:
                        isockstream (): ios (0) {}
                        isockstream(streambuf* sb): ios (sb) {}
};


On HP-UX11.00 with gcc3.0.2 I get the following errors.
Could someone please tell me what to include to get it working in the new
environment:

#include <iostream>
using namespace std;

class isockstream: public istream {
public:
                        isockstream (): ios (0) {}
                        isockstream(streambuf* sb): ios (sb) {}
                        
};

sstream.h: In constructor `isockstream::isockstream()':
sstream.h:6: no matching function for call to `std::basic_istream<char,
std::char_traits<char> >::basic_istream()'
/usr/local/include/g++-v3/bits/std_istream.h:209: candidates are: 
   std::basic_istream<_CharT, _Traits>::basic_istream(const 
   std::basic_istream<_CharT, _Traits>&) 
      [with _CharT = char, _Traits = std::char_traits<char>]
/usr/local/include/g++-v3/bits/std_istream.h:72:                 
   std::basic_istream<_CharT,
_Traits>::basic_istream(std::basic_streambuf<_CharT, _Traits>*) 
      [with _CharT = char, _Traits = std::char_traits<char>]


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