Server client og lign..

Jeg har et lille problem..
Altså jeg har en Server

Serveren spørger om du vil skrive til en fil.
Du skal svare ja / nej
når du har gjort det kan jeg ikke finde ud af hvordan man sletter det gamle indhold af stringen og vil have brugeren til at skrive nyt indhold ned i tekst dokumentet..

Server clienten:

#include "socket.h"
#include <process.h>
#include <string>
#include <iostream>
#include <sstream>
#include <windows.h>
#include <stdio.h>
using namespace std;

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

ofstream Writefile;
ifstream Readfile;

  while (1) {
    std::string r = s->ReceiveLine();
    if (r.empty()) break;
    cout << "Command Recieved: " << r << "Executing command..." << endl;

    string::size_type n = r.find('*');
    if(n != string::npos)
    {
        s->SendLine("Connection established");
        cout << "User connected!" << endl;
    }
    else
    {
        s->SendLine("Ready to use");

        const char *p;
        p = r.c_str();
        if(p == "1")
        {
            Writefile.open("lektier.txt", ios::app);
            if(Writefile.is_open())
            {
                s->SendLine("Enter homeworks");
                cin.get();
                Writefile << p << endl;
                s->SendLine("Has been written to file");
            }
            else
            {
                s->SendLine("Could not open Text file!");
                exit(-1);
            }
        }


        if(p == "read")
        {
            Readfile.open("lektier.txt");
            string Input;
            if(Readfile.is_open())
            {
                while(!Readfile.eof())
                {
                    getline(Readfile, Input);
                    s->SendLine(Input);
                    cout << Input << endl;
                }
            }

            else

            {
                s->SendLine("Error reading Text file");
                cout << "Error.." << endl;
            }
        }


    }


  }

  delete s;

  return 0;
}

int main(int argc, char* argv[]) {

string PORT;
int portNumber;
bool success;

cout << "Enter port to listen on: ";
while(!success)
{
    getline(cin, PORT);
    stringstream SS(PORT);
    success = SS >> portNumber;

    if(!success)
    {
        cout << "Invalid port number" << endl;
    }
}
system("cls");
cout << "Listening on port: " << portNumber << endl;
SocketServer in(portNumber, 5);

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

    unsigned ret;
    _beginthreadex(0,0,Answer,(void*) s,0,&ret);
  }

  return 0;
}

User clienten:

#include "socket.h"
#include <process.h>
#include <string>
#include <iostream>
#include <sstream>
#include <windows.h>
#include <stdio.h>
using namespace std;

int main() {
SetConsoleTitle("Christian Command Client");

string IP, PORT;
const char *ipAddress;
int port;
bool success;

cout << "Enter IP address to connect to: ";
getline(cin, IP);
ipAddress = IP.c_str();
cout << endl << "Enter Port: ";
while(!success)
{
    getline(cin, PORT);
    stringstream SS(PORT);
    success = SS >> port;

    if(!success)
    {
        cout << "Could not connect to port.." << endl;
    }
}

system("cls");
cout << "Ip: " << IP << endl;
cout << "Port: " << port << endl;



  try {
    SocketClient s(ipAddress, port);

    s.SendLine("*");

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

      string answer;
      string InputHomeworks;


      cout << "Would you like to Write new homeworks? Yes / No" << endl;
      getline(cin, answer);
      if(answer == "Yes" || answer == "yes")
      {
          system("cls");
          cout << "Enter new homeworks" << endl;
          getline(cin, InputHomeworks);
          s.SendLine(InputHomeworks);
      }

      cout << "Would you like to Read homeworks? Yes / No" << endl;
      getline(cin, answer);
      if(answer == "Yes" || answer == "yes")
      {




    }

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

  return 0;
}

Koden er ikke skrevet færdigt endnu fordi jeg er gået død i hvordan man kan skrive mere til samme string senere..

Det er helveds svært at forklare, men håber i forstår det.