//Data link layer function to receive a data frame or an ack from server.
//Also simulates the physical layer receive funtion.
//The data frame received contains an ack in its payload.
int dll_recv_py(int sock, Frame* frame, Ack* ack)
{
//Set up the receive buffer.
int size = 150;
ssize_t numBytes = 0;
char buffer[size];
//Use recv() funtion to receive from server.
numBytes = recv(sock, buffer, size, 0);
vector<char> objBuf;
for(int i=0; i<numBytes; i++)
{
objBuf.push_back(buffer[i]);
}
//Check the frame type field to determie whether it's a data frame or an ack.
//If it's an ack, return 0, if it's a data frame, return 1.
if(objBuf.at(2) == 'a')
{
Ack tempAck;
*ack = tempAck.reconstruct(objBuf);
return 0;
}
else
{
Frame tempFrame;
*frame = tempFrame.reconstruct(objBuf);
return 1;
}
}
//Data link layer function to send Ack data frame to network layer.
//Also simulates the check in network layer.
int dll_send_nwl(Frame frame, bool* breakFlg, int seqNum, bool ieop)
{
//Get the ack from the data frame.
Ack ack;
ack = ack.reconstruct(frame.getDataField());
//If the ack is correct.
if(ack.reconstruct(frame.getDataField()).isCorrect(seqNum))
{
//If this frame is the end of photo, set the break flag.
if(ieop)
{
*breakFlg = true;
}
nwl = true;
dll = false;
return 1;
}
//If the ack is not correct, return -1.
else
{
return -1;
}
}