AT Commands sent to USB Modem

Question

Hi,
I am trying to send AT commands to a USB modem using VC++. I found the code below online and have tried using it. I do not get any errors but it doesn't appear to be working.
I used Putty to set AT+CMGF= 0. However after I run this code, when I check the value of AT+CMGF it is still 0, so although no error is being thrown up, it doesn't seem to be sending correctly.
Any help would be great thanks.
#include <iostream>
#include <Windows.h>
#include <string.h>
using std::string;
int main() {
std::string data = "AT+CMGF=1";
 DCB dcb; 
 DWORD byteswritten; 
 HANDLE hPort = CreateFile( 
 "COM3", //"\\\\.\\COM10"
 GENERIC_WRITE | GENERIC_READ, 
 FILE_SHARE_READ| FILE_SHARE_WRITE, 
 NULL, 
 OPEN_EXISTING, 
 0, 
 NULL 
 DWORD dwerror = GetLastError();
 if (GetCommState(hPort,&dcb) == 0) {
return false; }
 dcb.BaudRate = CBR_9600; //9600 Baud 
 dcb.ByteSize = 8; //8 data bits 
 dcb.Parity = NOPARITY; //no parity 
 dcb.StopBits = ONESTOPBIT; //1 stop 
 if (!SetCommState(hPort,&dcb)) 
 return false; 
 bool retVal = WriteFile(hPort,&data,200,&byteswritten,NULL);
 dwerror = GetLastError();
 CloseHandle(hPort); //close the handle 
 return retVal; 

Answer 1

SOLVED: just needed to add \r\n after my commands
Okay, not solved! The first command, setting CMGF=1 works, nothing else seems to go through though. i.e. if CMGF is 0 and i run this code setting it to 1, it changes to 1 when I check the value in putty. 
I'm not sure if im doing something wrong in the way I send the CMGS and text message commands.
No errors come up...but the text message isn't sent. I send the CMGF and CMGS commands followed by a carriage return and the text message content followed by the SUB (CTRL+Z). doesn't seem to work. If I try reading the serial port using ReadFile() it
just hangs without setting a timeout. Any help would be appreciated. 
#include <iostream>
#include <Windows.h>
#include <string.h>
using namespace std;
int main() {
string CR;
CR = 13;
string SUB;
SUB = 26;
string mode = "AT+CMGF=1";  //+ CR; // \r";
mode.append(CR);
string phone = "AT+CMGS=\"0430554519\"" ; // \r";
phone.append(CR);
string message = "> Test C++ message " ;
message.append(SUB);
 DCB dcb; 
 DWORD byteswritten1; 
 DWORD byteswritten2; 
 DWORD byteswritten3; 
 DWORD byteswritten4; 
 DWORD byteswritten5; 
 DWORD byteswritten6; 
 HANDLE hPort = CreateFile( 
 "COM3",
 GENERIC_WRITE | GENERIC_READ, 
 FILE_SHARE_READ| FILE_SHARE_WRITE, 
 NULL, 
 OPEN_EXISTING, 
 0, 
 NULL 
 DWORD dwerror = GetLastError();
 if (GetCommState(hPort,&dcb) == 0) {
return false; }
 dcb.BaudRate = CBR_9600; //9600 Baud 
 dcb.ByteSize = 8; //8 data bits 
 dcb.Parity = NOPARITY; //no parity 
 dcb.StopBits = ONESTOPBIT; //1 stop 
 if (!SetCommState(hPort,&dcb)) 
 return false; 
  char UitBuff1[25];
DWORD dwBytesRead;
 bool retVal = WriteFile(hPort,&mode,mode.capacity(),&byteswritten1,NULL);
  retVal = WriteFile(hPort,&CR,CR.capacity(),&byteswritten2,NULL); 
 bool retVal1 = WriteFile(hPort,&phone,phone.capacity(),&byteswritten3,NULL);
  retVal = WriteFile(hPort,&CR,CR.capacity(),&byteswritten4,NULL);
 bool retVal2 = WriteFile(hPort,&message,message.capacity(),&byteswritten5,NULL);
  retVal = WriteFile(hPort,&CR,CR.capacity(),&byteswritten6,NULL);
  dwerror = GetLastError();
CloseHandle(hPort); //close the handle 
 return retVal;