Client/Server communication via sockets

The following is a simple Client Server example that actually covers quite a few different topics. The code is modified from the MadWizard.org Winsock Tutorial. It may be a good idea to go through the StringStreams example here and C/C++ String differences example here.

Please note that the code below is not the best example of coding practice.

Server code:

//Original Client-Server code from www.MadWizard.org
//Part of the Winsock networking tutorial by Thomas Bleeker
//Modified and tested on Microsoft Visual Studio 2008 - Zahid Ghadialy

#include <iostream>
#include <string>
#include <sstream>

#define WIN32_MEAN_AND_LEAN
#include <winsock2.h>
#include <windows.h>

//Add ws2_32.lib in Properties->Linker->Input->Additional Dependencies

using namespace std;

const int  REQ_WINSOCK_VER   = 2; // Minimum winsock version required
const int  DEFAULT_PORT      = 4444; 
const int  TEMP_BUFFER_SIZE  = 128;

//Forward Declarations
bool RunServer(int portNumber);

//MAIN
int main()
{ 
 int iRet = 1;
 WSADATA wsaData;

  cout << "SERVER STARTED" << endl;
 cout << "Initializing winsock... ";

 if (WSAStartup(MAKEWORD(REQ_WINSOCK_VER,0), &wsaData)==0)
 {
  // Check if major version is at least REQ_WINSOCK_VER
  if (LOBYTE(wsaData.wVersion) >= REQ_WINSOCK_VER)
  {
   cout << "initialized.\n";
   
   int port = DEFAULT_PORT;
   iRet = !RunServer(port);
  }
  else
  {
   cerr << "required version not supported!";
  }

  cout << "Cleaning up winsock... ";

  // Cleanup winsock
  if (WSACleanup()!=0)
  {
   cerr << "cleanup failed!\n";
   iRet = 1;
  }   
  cout << "done.\n";
 }
 else
 {
  cerr << "startup failed!\n";
 }
 return iRet;
}


string GetHostDescription(const sockaddr_in &sockAddr)
{
 ostringstream stream;
 stream << inet_ntoa(sockAddr.sin_addr) << ":" << ntohs(sockAddr.sin_port);
 return stream.str();
}

void SetServerSockAddr(sockaddr_in *pSockAddr, int portNumber)
{
 // Set family, port and find IP
 pSockAddr->sin_family = AF_INET;
 pSockAddr->sin_port = htons(portNumber);
 pSockAddr->sin_addr.S_un.S_addr = INADDR_ANY;
}

void HandleConnection(SOCKET hClientSocket, const sockaddr_in &sockAddr)
{
 // Print description (IP:port) of connected client
 cout << "Connected with " << GetHostDescription(sockAddr) << ".\n";
  exception e;

 char tempBuffer[TEMP_BUFFER_SIZE];

 // Read data
 while(true)
 {
  int retval;
  retval = recv(hClientSocket, tempBuffer, sizeof(tempBuffer), 0);
  if (retval==0)
  { 
   break; // Connection has been closed
  }
  else if (retval==SOCKET_ERROR)
  {
   exception e("socket error while receiving.");
      throw e;
  }
  else
  {
      string tempBufferString(tempBuffer);
      cout<<"Received over the socket :"<<tempBufferString<<endl;
      string tempString = "Loopbacked: " + tempBufferString + '\0';
      strcpy_s(tempBuffer, tempString.length() + 1, tempString.c_str());
   if (send(hClientSocket, tempBuffer, strlen(tempBuffer)+1, 0)==SOCKET_ERROR)
    {
     exception e("socket error while sending.");
        throw e;
    }
  }
 }
 cout << "Connection closed.\n";
}

bool RunServer(int portNumber)
{
 SOCKET hSocket = INVALID_SOCKET, hClientSocket = INVALID_SOCKET;
 bool bSuccess = true;
 sockaddr_in sockAddr = {0};
 
 try
 {
  // Create socket
  cout << "Creating socket... ";
  if ((hSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET)
    {
      cout << "failed Creating socket... \n";
      return false;
    }
  cout << "created.\n";
  
  // Bind socket
  cout << "Binding socket... ";
  SetServerSockAddr(&sockAddr, portNumber);
  if (bind(hSocket, reinterpret_cast<sockaddr*>(&sockAddr), sizeof(sockAddr))!=0)
    {
      cout << "failed Binding socket... \n";
      return false;
    }
  cout << "bound.\n";

  // Put socket in listening mode
  cout << "Putting socket in listening mode... ";
  if (listen(hSocket, SOMAXCONN)!=0)
    {
      cout << "failed Putting socket in listening mode... \n";
      return false;
    }
  cout << "done.\n";

  // Wait for connection
  cout << "Waiting for incoming connection... ";
  
  sockaddr_in clientSockAddr;
  int clientSockSize = sizeof(clientSockAddr);
  
  // Accept connection:
  hClientSocket = accept(hSocket,
       reinterpret_cast<sockaddr*>(&clientSockAddr),
       &clientSockSize);
 
  // Check if accept succeeded
  if (hClientSocket==INVALID_SOCKET)
    {
      cout << "accept function failed... \n";
      return false;
    }
  cout << "accepted.\n";
 
  // Wait for and accept a connection:
  HandleConnection(hClientSocket, clientSockAddr);

 }
 catch(exception& e)
 {
  cerr << "\nError: " << e.what() << endl;
  bSuccess = false; 
 }

 if (hSocket!=INVALID_SOCKET)
  closesocket(hSocket);
 
 if (hClientSocket!=INVALID_SOCKET)
  closesocket(hClientSocket);
  
 return bSuccess;
} 

Client code:

//Original Client-Server code from www.MadWizard.org
//Part of the Winsock networking tutorial by Thomas Bleeker
//Modified and tested on Microsoft Visual Studio 2008 - Zahid Ghadialy

#include <iostream>
#include <sstream>

#define WIN32_MEAN_AND_LEAN
#include <winsock2.h>
#include <windows.h>

using namespace std;

//Add ws2_32.lib in Properties->Linker->Input->Additional Dependencies

using namespace std;

const int  REQ_WINSOCK_VER   = 2; // Minimum winsock version required
const char DEF_SERVER_NAME[] = "127.0.0.1"; //localhost - can be your server name like "www.google.com"
const int  SERVER_PORT       = 4444; 
const int  TEMP_BUFFER_SIZE  = 128;

// IP number typedef for IPv4
typedef unsigned long IPNumber;

//Forward Declarations
bool RunClient(const char *pServername);

//MAIN
int main(int argc, char* argv[])
{
 int iRet = 1;
 WSADATA wsaData;

  cout << "CLIENT STARTED" << endl;
 cout << "Initializing winsock... ";

 if (WSAStartup(MAKEWORD(REQ_WINSOCK_VER,0), &wsaData)==0)
 {
  // Check if major version is at least REQ_WINSOCK_VER
  if (LOBYTE(wsaData.wVersion) >= REQ_WINSOCK_VER)
  {
   cout << "initialized.\n";
   
   // Set default hostname:
   const char *pHostname = DEF_SERVER_NAME;
   iRet = !RunClient(pHostname);
  }
  else
  {
   cerr << "required version not supported!";
  }

  cout << "Cleaning up winsock... ";

  // Cleanup winsock
  if (WSACleanup()!=0)
  {
   cerr << "cleanup failed!\n";
   iRet = 1;
  }   
  cout << "done.\n";
 }
 else
 {
  cerr << "startup failed!\n";
 }
 return iRet;
}


IPNumber FindHostIP(const char *pServerName)
{
 HOSTENT *pHostent;

 // Get hostent structure for hostname:
 if (!(pHostent = gethostbyname(pServerName)))
  {
    exception e("could not resolve hostname.");
    throw e;
  }
 
 // Extract primary IP address from hostent structure:
 if (pHostent->h_addr_list && pHostent->h_addr_list[0])
  return *reinterpret_cast<IPNumber*>(pHostent->h_addr_list[0]);
 
 return 0;
}

void FillSockAddr(sockaddr_in *pSockAddr, const char *pServerName, int portNumber)
{
 // Set family, port and find IP
 pSockAddr->sin_family = AF_INET;
 pSockAddr->sin_port = htons(portNumber);
 pSockAddr->sin_addr.S_un.S_addr = FindHostIP(pServerName);
}

bool RunClient(const char *pServername)
{
 SOCKET     hSocket = INVALID_SOCKET;
 char      tempBuffer[TEMP_BUFFER_SIZE];
 sockaddr_in sockAddr = {0};
 bool      bSuccess = true;
 
 try
 {
  // Lookup hostname and fill sockaddr_in structure:
  cout << "Looking up hostname " << pServername << "... ";
  FillSockAddr(&sockAddr, pServername, SERVER_PORT);
  cout << "found.\n";
 
  // Create socket
  cout << "Creating socket... ";
  if ((hSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET)
    {
      cout<<"could not create socket. "<<endl;
      return false;
    }
  cout << "created.\n";
  
  // Connect to server
  cout << "Attempting to connect to " << inet_ntoa(sockAddr.sin_addr)
       << ":" << SERVER_PORT <<  "... ";
  if (connect(hSocket, reinterpret_cast<sockaddr*>(&sockAddr), sizeof(sockAddr))!=0)
    {
      cout<<"could not connect. "<<endl;
      return false;
    }
  cout << "connected.\n";
  
  cout << "Sending requests and checking for loopbacks... "<<endl;

    //Lets sent 100 packets and get it looped back from Server
    for(int i = 0; i < 10; i++)
    {
      int retval = 0;
      stringstream ss (stringstream::in | stringstream::out);
      ss << "Message " << i <<"\n";

      std::string s = ss.str() + '\0'; //Adding the null charachter
      if (send(hSocket, s.c_str(), s.size() + 1, 0)==SOCKET_ERROR)
      {
        cout<<"failed to send data. "<<endl;
        return false;
      }

      retval = recv(hSocket, tempBuffer, sizeof(tempBuffer), 0);
      if (retval==0)
      {
        cout<<"Connection closed"<<endl;
        break;
      }
      else if (retval==SOCKET_ERROR)
      {
        exception e("socket error while receiving.");
        throw e;
      }
      else
      {
    // retval is number of bytes read
    // Terminate buffer with zero and print as string
    tempBuffer[retval] = 0;
        cout << "Received " << retval << " bytes. Received : " <<tempBuffer;
      }
    }  
 }
 catch(exception& e)
 {
  cerr << "\nError: " << e.what() << endl;
  bSuccess = false; 
 }

 if (hSocket!=INVALID_SOCKET)
 {
  closesocket(hSocket);
 }
 return bSuccess;
} 

The Server Output is as follows:

The Client output is as follows: