C++ Socket Class for Windows

 

Here, I present the source code for a socket class that faciliates using Sockets in Windows Programming.  This socket class is being used for BROADCAST chat client. These are actually four classes: Socket (the base class) from which SocketServer and SocketClient are derived. Also, there is SocketSelect which can be used to do a Select call on more than one Socket. The constructors of Socket are protected; this should be a taken as a hint not to use Socket, but either SocketServer or SocketClient. When you compile this files, make sure you link them against Ws2_32.lib.  A small description of the socket class: Every program that uses Windows Sockets needs to call WSAStartup. This call is wrapped into Socket::Start, which in turn is called by the Socket's constructor. I pass 2.0 as version here as I expect that version to be installed.
The Socket's constructor also calls socket() (note the small s) which actually creates the socket. It passes the SOCK_STREAM parameter, indicating TCP. If UDP were wished, you'd have to pass SOCK_DGRAM. SocketClient: SocketClient is inherited from Socket.
The constructor of SocketClient takes a host as parameter, which is the name of the server that this client wishes to communicate to. This name is resolved into an IP Address by gethostbyname(). SocketServer: SocketServer is inherited from Socket.
The constructor of the SocketServer class listens on the port indicated in its parameter. This is made by calling bind().
As SOCK_STREAM type sockets have the ability to queue incoming connection requests, we need to know the maximum number of connections to be queued which can be stated by the connections parameter (and which is passed to listen()).
SocketServer::Accept(): simply waits for an incoming connection request (or removes one from the queue) by calling accept (note the small a).
The header file
socket.h
/*
   Socket.h

   Copyright (C) 2002-2004 René Nyffenegger

   This source code is provided 'as-is', without any express or implied
   warranty. In no event will the author be held liable for any damages
   arising from the use of this software.

   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:

   1. The origin of this source code must not be misrepresented; you must not
      claim that you wrote the original source code. If you use this source code
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.

   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original source code.

   3. This notice may not be removed or altered from any source distribution.

   René Nyffenegger [e-mail]
*/

#ifndef SOCKET_H
#define SOCKET_H

#include <WinSock2.h>

#include <string>

enum TypeSocket {BlockingSocket, NonBlockingSocket};

class Socket {
public:

  virtual ~Socket();
  Socket(const Socket&);
  Socket& operator=(Socket&);

  std::string ReceiveLine();
  std::string ReceiveBytes();

  void   Close();

  // The parameter of SendLine is not a const reference
  // because SendLine modifes the std::string passed.
  void   SendLine (std::string);

  // The parameter of SendBytes is a const reference
  // because SendBytes does not modify the std::string passed
  // (in contrast to SendLine).
  void   SendBytes(const std::string&);

protected:
  friend class SocketServer;
  friend class SocketSelect;

  Socket(SOCKET s);
  Socket();

  SOCKET s_;

  int* refCounter_;

private:
  static void Start();
  static void End();
  static int  nofSockets_;
};

class SocketClient : public Socket {
public:
  SocketClient(const std::string& host, int port);
};

class SocketServer : public Socket {
public:
  SocketServer(int port, int connections, TypeSocket type=BlockingSocket);

  Socket* Accept();
};

// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/wsapiref_2tiq.asp
class SocketSelect {
  public:
    SocketSelect(Socket const * const s1, Socket const * const s2=NULL, TypeSocket type=BlockingSocket);

    bool Readable(Socket const * const s);

  private:
    fd_set fds_;
};

 

#endif
The implementation file
socket.cpp
/*
   Socket.cpp

   Copyright (C) 2002-2004 René Nyffenegger

   This source code is provided 'as-is', without any express or implied
   warranty. In no event will the author be held liable for any damages
   arising from the use of this software.

   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:

   1. The origin of this source code must not be misrepresented; you must not
      claim that you wrote the original source code. If you use this source code
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.

   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original source code.

   3. This notice may not be removed or altered from any source distribution.

   René Nyffenegger [e-mail]
*/

#include "Socket.h"
#include <iostream>

using namespace std;

int Socket::nofSockets_= 0;

void Socket::Start() {
  if (!nofSockets_) {
    WSADATA info;
    if (WSAStartup(MAKEWORD(2,0), &info)) {
      throw "Could not start WSA";
    }
  }
  ++nofSockets_;
}

void Socket::End() {
  WSACleanup();
}

Socket::Socket() : s_(0) {
  Start();
  // UDP: use SOCK_DGRAM instead of SOCK_STREAM
  s_ = socket(AF_INET,SOCK_STREAM,0);

  if (s_ == INVALID_SOCKET) {
    throw "INVALID_SOCKET";
  }

  refCounter_ = new int(1);
}

Socket::Socket(SOCKET s) : s_(s) {
  Start();
  refCounter_ = new int(1);
};

Socket::~Socket() {
  if (! --(*refCounter_)) {
    Close();
    delete refCounter_;
  }

  --nofSockets_;
  if (!nofSockets_) End();
}

Socket::Socket(const Socket& o) {
  refCounter_=o.refCounter_;
  (*refCounter_)++;
  s_         =o.s_;

  nofSockets_++;
}

Socket& Socket::operator=(Socket& o) {
  (*o.refCounter_)++;

  refCounter_=o.refCounter_;
  s_         =o.s_;

  nofSockets_++;

  return *this;
}

void Socket::Close() {
  closesocket(s_);
}

std::string Socket::ReceiveBytes() {
  std::string ret;
  char buf[1024];
 
  while (1) {
    u_long arg = 0;
    if (ioctlsocket(s_, FIONREAD, &arg) != 0)
      break;

    if (arg == 0)
      break;

    if (arg > 1024) arg = 1024;

    int rv = recv (s_, buf, arg, 0);
    if (rv <= 0) break;

    std::string t;

    t.assign (buf, rv);
    ret += t;
  }
 
  return ret;
}

std::string Socket::ReceiveLine() {
  std::string ret;
  while (1) {
    char r;

    switch(recv(s_, &r, 1, 0)) {
      case 0: // not connected anymore;
              // ... but last line sent
              // might not end in \n,
              // so return ret anyway.
        return ret;
      case -1:
        return "";
//      if (errno == EAGAIN) {
//        return ret;
//      } else {
//      // not connected anymore
//      return "";
//      }
    }

    ret += r;
    if (r == '\n')  return ret;
  }
}

void Socket::SendLine(std::string s) {
  s += '\n';
  send(s_,s.c_str(),s.length(),0);
}

void Socket::SendBytes(const std::string& s) {
  send(s_,s.c_str(),s.length(),0);
}

SocketServer::SocketServer(int port, int connections, TypeSocket type) {
  sockaddr_in sa;

  memset(&sa, 0, sizeof(sa));

  sa.sin_family = PF_INET;            
  sa.sin_port = htons(port);         
  s_ = socket(AF_INET, SOCK_STREAM, 0);
  if (s_ == INVALID_SOCKET) {
    throw "INVALID_SOCKET";
  }

  if(type==NonBlockingSocket) {
    u_long arg = 1;
    ioctlsocket(s_, FIONBIO, &arg);
  }

  /* bind the socket to the internet address */
  if (bind(s_, (sockaddr *)&sa, sizeof(sockaddr_in)) == SOCKET_ERROR) {
    closesocket(s_);
    throw "INVALID_SOCKET";
  }
 
  listen(s_, connections);                              
}

Socket* SocketServer::Accept() {
  SOCKET new_sock = accept(s_, 0, 0);
  if (new_sock == INVALID_SOCKET) {
    int rc = WSAGetLastError();
    if(rc==WSAEWOULDBLOCK) {
      return 0; // non-blocking call, no request pending
    }
    else {
      throw "Invalid Socket";
    }
  }

  Socket* r = new Socket(new_sock);
  return r;
}

SocketClient::SocketClient(const std::string& host, int port) : Socket() {
  std::string error;

  hostent *he;
  if ((he = gethostbyname(host.c_str())) == 0) {
    error = strerror(errno);
    throw error;
  }

  sockaddr_in addr;
  addr.sin_family = AF_INET;
  addr.sin_port = htons(port);
  addr.sin_addr = *((in_addr *)he->h_addr);
  memset(&(addr.sin_zero), 0, 8);

  if (::connect(s_, (sockaddr *) &addr, sizeof(sockaddr))) {
    error = strerror(WSAGetLastError());
    throw error;
  }
}

SocketSelect::SocketSelect(Socket const * const s1, Socket const * const s2, TypeSocket type) {
  FD_ZERO(&fds_);
  FD_SET(const_cast<Socket*>(s1)->s_,&fds_);
  if(s2) {
    FD_SET(const_cast<Socket*>(s2)->s_,&fds_);
  }    

  TIMEVAL tval;
  tval.tv_sec  = 0;
  tval.tv_usec = 1;

  TIMEVAL *ptval;
  if(type==NonBlockingSocket) {
    ptval = &tval;
  }
  else {
    ptval = 0;
  }

  if (select (0, &fds_, (fd_set*) 0, (fd_set*) 0, ptval) == SOCKET_ERROR)
    throw "Error in select";
}

bool SocketSelect::Readable(Socket const* const s) {
  if (FD_ISSET(s->s_,&fds_)) return true;
  return false;
}
A simple Client
The following simple client connects to www.google.ch and get its front-website.
#include "Socket.h"

#include <iostream>

using namespace std;

int main() {

  try {
    SocketClient s("www.google.com", 80);

    s.SendLine("GET / HTTP/1.0");
    s.SendLine("Host: www.google.com");
    s.SendLine("");

    while (1) {
      string l = s.ReceiveLine();
      if (l.empty()) break;
      cout << l;
      cout.flush();
    }

  }
  catch (const char* s) {
    cerr << s << endl;
  }
  catch (std::string s) {
    cerr << s << endl;
  }
  catch (...) {
    cerr << "unhandled exception\n";
  }

  return 0;
}
A simple echo Server
The following simple Server opens a port on 2000 and waits for incoming connections. Each connection is answered with the same line as was written (echoed). If you want to test the server, use telnet localhost 2000
/*
   EchoServer.cpp

   Copyright (C) 2002-2004 René Nyffenegger

   This source code is provided 'as-is', without any express or implied
   warranty. In no event will the author be held liable for any damages
   arising from the use of this software.

   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:

   1. The origin of this source code must not be misrepresented; you must not
      claim that you wrote the original source code. If you use this source code
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.

   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original source code.

   3. This notice may not be removed or altered from any source distribution.

   René Nyffenegger [e-mail]
*/

#include "Socket.h"
#include <process.h>
#include <string>

unsigned __stdcall Answer(void* a) {
  Socket* s = (Socket*) a;

  while (1) {
    std::string r = s->ReceiveLine();
    if (r.empty()) break;
    s->SendLine(r);
  }

  delete s;

  return 0;
}

int main(int argc, char* argv[]) {
  SocketServer in(2000,5);

  while (1) {
    Socket* s=in.Accept();

    unsigned ret;
    _beginthreadex(0,0,Answer,(void*) s,0,&ret);
  }
 
  return 0;
}
A Proxy that uses the Socket class
You need the Chameleon class to compile this proxy. Usage: proxy <port proxy> <addr server> <port server>.
This proxy will then listen on <port proxy> and whenever it receives a connection, relays the traffic to the <port server> of <addr server>. This makes it ideal to see what an SMTP Client exchanges with a SMTP Server, or equally what a NNTP client exchanges with an NNTP Server.
Proxy.cpp
/*
   Proxy.cpp

   Copyright (C) 2002-2004 René Nyffenegger

   This source code is provided 'as-is', without any express or implied
   warranty. In no event will the author be held liable for any damages
   arising from the use of this software.

   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:

   1. The origin of this source code must not be misrepresented; you must not
      claim that you wrote the original source code. If you use this source code
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.

   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original source code.

   3. This notice may not be removed or altered from any source distribution.

   René Nyffenegger [e-mail]
*/

#include "Socket.h"

#include <iostream>
#include <process.h>
#include <sstream>

int         portProxy;
std::string addrServer;
int         portServer;

unsigned __stdcall RunProxyThread (void* a) {
  Socket*      s = (Socket*) a;
  SocketClient c(addrServer, portServer);

  while (1) {
    SocketSelect sel(s, &c);

    bool still_connected = true;

    if (sel.Readable(s)) {
      std::string bytes = s->ReceiveBytes();
      c.SendBytes(bytes);
      std::cout << "Server: " << bytes << std::endl;
      if (bytes.empty()) still_connected=false;
    }
    if (sel.Readable(&c)) {
      std::string bytes = c.ReceiveBytes();
      s->SendBytes(bytes);
      std::cout << "Client: " << bytes << std::endl;
      if (bytes.empty()) still_connected=false;
    }
    if (! still_connected) {
      break;
    }
  }

  delete s;

  return 0;
}

int main(int argc, char* argv[]) {
  if (argc < 4) {
    std::cout << "Usage:" << std::endl;
    std::cout << "  proxy <port proxy> <addr server> <port server>" << std::endl;
    std::cout << std::endl;
    std::cout << "  This proxy will then listen on <port proxy> and whenever it receives" << std::endl;
    std::cout << "  a connection, relays the traffic to the <port server> of <addr server>." << std::endl;
    std::cout << "  This makes it ideal to see what an SMTP Client exchanges with a SMTP Server," << std::endl;
    std::cout << "  or equally what a NNTP client exchanges with an NNTP Server." << std::endl << std::endl;
    return -1;
  }

  std::stringstream s;
 
  s<<argv[1]; s>>portProxy; s.clear();

  addrServer=argv[2];

  s<<argv[3]; s>>portServer;

  SocketServer in(portProxy,5);

  while (1) {
    Socket* s=in.Accept();

    unsigned ret;
    _beginthreadex(0, 0, RunProxyThread,(void*) s,0,&ret);
  }
 
  return 0;
}
See also: Fiddler: a HTTP Debugging Proxy which logs all HTTP traffic between your computer and the Internet. Fiddler allows you to watch HTTP Traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler is designed to be much simpler than using NetMon or Achilles.
Message Distributor
Message Distributor is a server that listens on port 2000. Any number of clients can connect to that server. When a client sends a message to the server, the server will broadcast this message to all other clients, but not to the one that sent the message.
MsgDistributor.cpp
/*
   MsgDistributor.cpp

   Copyright (C) 2002-2004 René Nyffenegger

   This source code is provided 'as-is', without any express or implied
   warranty. In no event will the author be held liable for any damages
   arising from the use of this software.

   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:

   1. The origin of this source code must not be misrepresented; you must not
      claim that you wrote the original source code. If you use this source code
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.

   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original source code.

   3. This notice may not be removed or altered from any source distribution.

   René Nyffenegger [e-mail]
*/

#include "Socket.h"
#include <process.h>
#include <string>
#include <list>

typedef std::list<Socket*> socket_list;

socket_list g_connections;

unsigned __stdcall Connection(void* a) {
  Socket* s = (Socket*) a;

  g_connections.push_back(s);

  s->SendLine("Welcome to the Message Distributor");

  while (1) {
    std::string r = s->ReceiveLine();
    if (r.empty()) break;

    for (socket_list::iterator os =g_connections.begin();
                               os!=g_connections.end();
                               os++) {
      if (*os != s) (*os)->SendLine(r);
    }
  }

  g_connections.remove(s);

  delete s;

  return 0;
}

int main() {
  SocketServer in(2000,5);
 
  while (1) {
    Socket* s=in.Accept();
 
    unsigned ret;
    _beginthreadex(0,0,Connection,(void*) s,0,&ret);
  }
 
  return 0;
}
The file list:

socket.h
Chameleon.h
Chameleon.cpp
EchoServer.cpp
MsgDistributor.cpp
Proxy.cpp
Socket.cpp
EchoServer.exe
Proxy.exe
makefile
I was able to compile the sources with mingw using the supplied makefile.
Thanks