Socket.cpp - A C++ Socket class for Windows

These are actually four classes: Socket (the base class), SocketServer and SocketClient (which two derive from which SocketServer) and 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.

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 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 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).

When compiling these files, make sure you link them against ws2_32.lib (or wsock32.lib?), at least with mingw, see compiling examples.

A few examples on using Socket.cpp can be found here.

This socket class is also used for the Simple C++ WebServer for Windows.

The source code is hosted in this github repository.

/* 
   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 rene.nyffenegger@adp-gmbh.ch
*/


#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;
}

/* 
   Socket.h

   Copyright (C) 2002-2017 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 rene.nyffenegger@adp-gmbh.ch
*/

#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();
};

class SocketSelect {
// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/wsapiref_2tiq.asp
  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

I also want to say thanks to Eugene Wee, Nathan Vander Wilt, Fabien Le Lez, http://www.infflux.com and Tamas Kaskoto who all have helped improve the source and the socket class in one way or another.