//==================================================== file = rawClient.c =====
//=  A message "client" program to demonstrate raw sockets programming        =
//=============================================================================
//=  Notes:                                                                   =
//=    1) This program compiles only for Winsock                              =
//=    2) This program needs rawServer to be running on another host.         =
//=       Program rawServer must be started first.                            =
//=    3) This program assumes that the IP address of the host running        =
//=       rawServer is defined in "#define IP_ADDR"                           =
//=    4) For Windows 7 needs to run in an elevated command window (cmd)      =
//=    5) If run locally (host to host on one machine) then rawClient will    =
//=       receive both the packet it sends (to rawServer) and the reply from  =
//=       rawServer. See the code block labeled as "DEBUG".                   =
//=---------------------------------------------------------------------------=
//=  Example execution: (rawServer and rawClient running on host 127.0.0.1)   =
//=   Received from server: 4500003755ae000080ff00007f0000017f000001 | Test   =
//=   message from CLIENT to SERVER                                           =
//=   Received from server: 4500004255af000080ff00007f0000017f000001 | This   =
//=   is a reply message from SERVER to CLIENT                                =
//=---------------------------------------------------------------------------=
//=  Build: bcc32 rawClient.c ws2_32.lib or cl rawClient.c ws2_32.lib         =
//=---------------------------------------------------------------------------=
//=  Execute: rawClient                                                       =
//=---------------------------------------------------------------------------=
//=  Author: Ken Christensen                                                  =
//=          University of South Florida                                      =
//=          WWW: http://www.csee.usf.edu/~christen                           =
//=          Email: christen@csee.usf.edu                                     =
//=---------------------------------------------------------------------------=
//=  History:  KJC (03/26/17) - Genesis (from udpClient.c and rawsend.c)      =
//=============================================================================
//----- Include files ---------------------------------------------------------
#include <stdio.h>          // Needed for printf()
#include <string.h>         // Needed for memcpy() and strcpy()
#include <stdlib.h>         // Needed for exit()
#include <windows.h>        // Needed for all Winsock stuff

//----- Defines ---------------------------------------------------------------
#define  PORT_NUM           1050    // Port number used
#define  IP_ADDR     "127.0.0.1"    // IP address of server1 (*** HARDWIRED ***)

//===== Main program ==========================================================
int main()
{
  WORD wVersionRequested = MAKEWORD(1,1);  // Stuff for WSA functions
  WSADATA wsaData;                         // Stuff for WSA functions
  int                  client_s;        // Client socket descriptor
  struct sockaddr_in   server_addr;     // Server Internet address
  int                  addr_len;        // Internet address length
  unsigned char        out_buf[4096];   // Output buffer for data
  unsigned char        in_buf[4096];    // Input buffer for data
  int                  retcode;         // Return code
  int                  i;               // Loop index

  // This stuff initializes winsock
  WSAStartup(wVersionRequested, &wsaData);

  // Create a raw socket
  client_s = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
  if (client_s < 0)
  {
    printf("*** ERROR - socket() failed \n");
    exit(-1);
  }

  // Fill-in server socket address information
  server_addr.sin_family = AF_INET;                 // Address family to use
  server_addr.sin_addr.s_addr = inet_addr(IP_ADDR); // IP address to use

  // Assign a message to buffer out_buf
  strcpy(out_buf, "Test message from CLIENT to SERVER");

  // Now send the message to server.  The "+ 1" is for the end-of-string
  // delimiter
  retcode = sendto(client_s, out_buf, (strlen(out_buf) + 1), 0,
    (struct sockaddr *)&server_addr, sizeof(server_addr));
  if (retcode < 0)
  {
    printf("*** ERROR - sendto() failed \n");
    exit(-1);
  }

  // Wait to receive a message
  addr_len = sizeof(server_addr);
  retcode = recvfrom(client_s, in_buf, sizeof(in_buf), 0,
    (struct sockaddr *)&server_addr, &addr_len);
  if (retcode < 0)
  {
    printf("*** ERROR - recvfrom() failed \n");
    exit(-1);
  }

  // Output the received message (IP header and then payload)
  printf("Received from server: ");
  for (i=0; i<20; i++)
    printf("%02x", in_buf[i]);
  printf(" | ");
  for(i=20; i<retcode; i++)
    printf("%c", in_buf[i]);
  printf("\n");

//===========================================================================
//== DEBUG: If sending from/to local host then first message received is   ==
//== "my" message, the second message is from the server and is received   ==
//== and is output below.                                                  ==
//===========================================================================
  // Wait to receive a message
  addr_len = sizeof(server_addr);
  retcode = recvfrom(client_s, in_buf, sizeof(in_buf), 0,
    (struct sockaddr *)&server_addr, &addr_len);
  if (retcode < 0)
  {
    printf("*** ERROR - recvfrom() failed \n");
    exit(-1);
  }

  // Output the received message (IP header and then payload)
  printf("Received from server: ");
  for (i=0; i<20; i++)
    printf("%02x", in_buf[i]);
  printf(" | ");
  for(i=20; i<retcode; i++)
    printf("%c", in_buf[i]);
  printf("\n");
//===========================================================================

  // Close all open sockets
  retcode = closesocket(client_s);
  if (retcode < 0)
  {
    printf("*** ERROR - closesocket() failed \n");
    exit(-1);
  }

  // This stuff cleans-up winsock
  WSACleanup();

  // Return zero and terminate
  return(0);
}