My first Webserver!,*cough*...kind of.

So this week I have been working on assignment 2, making a web server using C++ and Winsock2 API. It went quite well at the start and in basically one day I got a simple server (if you can call it that) that could handle one connection. I received data from the user and I displayed some text in the web browser to the user.

 

As you can see the browser in the back and in the front is the C++ console that shows the IP address of the user. I also show how many bytes I received and how many I sent. So far so good, but as you can see in the picture there are two new visitors from same IP address, that’s something I need to fix because right now I just grab anything I got, delete it and grab it again for some reason I have yet to figure out. I also I also don't handle time outs correctly and a bunch of other things but I don't care. It's a great feeling just getting something on screen. It made my day!

 Below is part of my main loop. First I had the myServer.listenOnSocket() function inside the loop but after asking our teacher Tommi how the listen() function for Winsock2 works I moved it out from the loop. Apparently the function opens up a listener for sockets that keep listening until closed. So it doesn't need to be in the loop since it keeps listening.

I then call my accept client function and accept the client and creates a client struct that holds all the data of the client, like the IP address and such. After that I call my update client connections which I want to use for updating retrieving and sending data as well as checking for time outs from the clients but I won't show that in detail because it's not working properly yet.

When I built this I thought about going around it like a game loop because a connection to a website/ server is in my mind is always open like a game that is always running.  Today I almost managed to handle multiple connections. The only trouble I have is when one new user connects the other one gets timed out. I'm not sure how to solve that but I will have to do some more code sniffing. So this post isn’t so analytic but I can’t help it because right now I’m just playing around with all the functions in this API trying to figure out how it all works.  Maybe I will dive deeper into this in my next post.

By the way, Last week I mentioned I had some problems with templates. This one:

template<typename T>               //this is the way I tried with no success

class LinkedList<T>;

and:

bool VerifyListErase(LinkedList<T> _List, const std::string& _Message);

Well apparently my error was not how I wrote these. They are all correct. The error was in a completely other place in the code. That’s the difficult thing with templates. I will use them more carefully in the future because the errors you get don’t make sense.

Back to programming!

Finally we started programming again and moved on from all that nonsense of playing board games and whatnot. Part of this course we need to write weekly blogs so I will be more active again.

So in this course we have 3 assignments.

Assignment 1 - Create a linked list and a Binary search tree. (Almost done with this)

Assignment 2 - Consists of writing a webserver

Assignment 3 - Create our own 3D game and engine using DirectX.

So this week I will share my thoughts on Assignment 1. So I actually did create a linked list and a binary search tree a few months ago with the help from youtube, especially from Paul Programming .

It's not very hard. The hard part is keeping track of your pointers.

This week we also learned how to use templates in programming to make our programming more generic. I still have problems using templates in a effective way but I gave it a try and made a linked list and BST (Binary search tree) with templates in mind. at first I got a bunch of errors that made no sense but I fast started to get a hand of how the syntax was supposed to look. Though I'm still struggling with some things, For example when working with normal classes you can forward declare instead of using #include "headername.h" you just write class classname; before the class where you want to use it, so I wrote this:

( class LinkedList;                         //normal way to write a forward declare )

template<typename T>               //this is the way I tried with no success

class LinkedList<T>;

template <typnename T>

class TestModule

{

public:

                  LinkedList();

                  ~LinkedList();

private:

........

........

}

So I still have to figure out how to do that and also another thing I had problem with was how to use another template as a function parameter in a function that is part of class template. Like so:

template <typnename T>

class TestModule

{

public:

bool VerifyListErase(LinkedList<T> _List, const std::string& _Message);

.........

.........

}

If you read this and know how to solve this please feel free to comment below. I will write here again when I find a good solution. It's probably not that hard.

Recursion

So on to what I liked about this week. Recursion! Using recursive functions can be really useful but sometimes they might be tricky to understand. It is basically a function that calls itself within the function creating a loop. 

Below is a search function I wrote that starts the search in the binary search tree from the node that is entered in and search through the whole tree/sub tree for a specific key/data. If a match is found the boolean variable _Match is set to true.

If no match is found the function calls itself and goes to the left and does the whole thing over again until it’s not possible to go left anymore. Then the function moves upwards one step and then tries to go right. It searches through every node until something is found or not found. 

It technically moves through the tree like the red numbers below show. If new to the concept it’s quite hard to grasp so I will try to explain it again.  What happens when a function calls itself is that it goes deeper and deeper until the end and then it returns up one step and does the next instruction. if there is no instruction it goes up another step and checks and so on.

So for example looking at the picture below and starting at 1 the function goes left every iteration until it can't go left more and when number 5 is reached and no match is found the function moves up one step to number 6 and then calls the function again but now with parameter to go right. So it goes to number 7, when nothing is found it moves up to number 8 and then 9 and then goes right again down to 10 and then back up and so on until all nodes have been searched..

If you want to see my code here is a link to Bitbucket. You can use my code freely but if something breaks it’s not my fault. J