Real Time Internet
Requirements:
• Knowledge of Net Commands
• String Manipulation Skills
Turing’s Net Drawbacks:
If you start playing around with Turing’s Net Features, you will realize that you can send one data over the net to another person really fast, but if you tried sending more then 1 variable, it would not work properly.
So what to do to fix it?
Since one variable can be sent through the Net module safely, we need to find a way to combine all the information we want to send over the net. One method would be to use tokenized strings. A tokenized string is a string that is part of a bigger string, separated by delimiters.
To put all the data into one string should not be hard as you can easily convert to string and add the delimiter after. I.e.
var c := intstr (px) + "/" + intstr (py)
If the Player X and Player Y variables both had the value 250, our string would be “250/250”. We will send this over the net to the receiver. This saves us from sending two variables: Player X and then Player Y.
Now we have a new problem: how do we read this information? I have made a sample Get_Token function to assist us.
| Turing: |
body fcn Get_Token var tmsg := msg var toks : flexible array 1 .. 1 of string var b := 1 if index (tmsg, del) = 0 then /* Checks if the delimeter is inside the string and if its not it will either result the message or if the token requested is > 1 then it will return null */ if num > 1 then result "null" else result tmsg end if else /* If its in the string then it will do the process of splitting the string apart into tokens*/ loop toks (b) := tmsg (1 .. index (tmsg, del) - 1) tmsg := tmsg (index (tmsg, del) + 1 .. *) exit when index (tmsg, del) = 0 b += 1 new toks, upper (toks) + 1 end loop b += 1 new toks, upper (toks) + 1 toks (b) := tmsg end if new toks, upper (toks) + 1 /* If the token requested is greater then the number of tokens it retruns null */ if num > b then result "null" else result toks (num) end if end Get_Token |
After we have sent the “250/250” string to our receiver, the receiver needs to read the tokens.
Token #1 results the X location and Token #2 results the Y location. This saves us from getting 2 variables from the net stream.
A slight drawback to this method is that Turing’s string's can be a maximum of 255 characters long, so you will have to be creative when sending the data. For example instead of base ten numbers like 15 you could send its hexadecimal value “F”. I will not get into detail here since that would require another tutorial.
I have attached a simple ball movement program in real time with two people.
Yes I could have used records but for simplicity I did not.
Example
| Turing: |
forward fcn Get_Token (msg : string, num : int, del : char) : string
/* Real Time Internet by Saad Ahmad */ /* Limits are 255 string limit */ var choice : int loop cls put "1 -> Host" put "2 -> Join" get choice exit when choice > 0 and choice < 3 end loop var stream : int var address : string const port := 5055 var px, py := 250 var msg := "250/250" /* Default Location for players */ var key : array char of boolean var p2x, p2y := 100 if choice = 1 then put "Your ip is ", Net.LocalAddress stream := Net.WaitForConnection (port, address) View.Set ("offscreenonly") loop var b := msg if Net.TokenAvailable (stream) then /* Checks if string is available */ get : stream, b : * end if Input.KeyDown (key) if key (KEY_UP_ARROW) then py += 10 end if if key (KEY_DOWN_ARROW) then py -= 10 end if if key (KEY_LEFT_ARROW) then px -= 10 end if if key (KEY_RIGHT_ARROW) then px += 10 end if p2x := strint (Get_Token (b, 1, "/")) /* Gets the location X which we made token #1 */ p2y := strint (Get_Token (b, 2, "/")) /* Gets the location Y which we made token #2 */ msg := b Draw.FillOval (px, py, 10, 10, red) var c := intstr (px) + "/" + intstr (py) /* Makes information one string and sends it */ put : stream, c Draw.FillOval (p2x, p2y, 10, 10, yellow) View.Update Time.DelaySinceLast (50) cls end loop end if if choice = 2 then var a : string put "Enter IP" get a stream := Net.OpenConnection (a, port) View.Set ("offscreenonly") if stream > 0 then loop var b := msg if Net.TokenAvailable (stream) then /* Checks if string is available */ get : stream, b : * end if msg := b Input.KeyDown (key) if key (KEY_UP_ARROW) then py += 10 end if if key (KEY_DOWN_ARROW) then py -= 10 end if if key (KEY_LEFT_ARROW) then px -= 10 end if if key (KEY_RIGHT_ARROW) then px += 10 end if p2x := strint (Get_Token (b, 1, "/")) /* Gets the location X which we made token #1 */ p2y := strint (Get_Token (b, 2, "/")) /* Gets the location Y which we made token #2 */ msg := b Draw.FillOval (px, py, 10, 10, red) var c := intstr (px) + "/" + intstr (py) /* Makes information one string and sends it */ put : stream, c Draw.FillOval (p2x, p2y, 10, 10, yellow) View.Update Time.DelaySinceLast (50) cls end loop end if end if /* Main body of Get_Token Tokens are just words in a string which are seperated by a delimeter */ body fcn Get_Token var tmsg := msg var toks : flexible array 1 .. 1 of string var b := 1 if index (tmsg, del) = 0 then /* Checks if the delimeter is inside the string and if its not it will either result the message or if the token requested is > 1 then it will return null */ if num > 1 then result "null" else result tmsg end if else /* If its in the string then it will do the process of splitting the string apart into tokens*/ loop toks (b) := tmsg (1 .. index (tmsg, del) - 1) tmsg := tmsg (index (tmsg, del) + 1 .. *) exit when index (tmsg, del) = 0 b += 1 new toks, upper (toks) + 1 end loop b += 1 new toks, upper (toks) + 1 toks (b) := tmsg end if new toks, upper (toks) + 1 /* If the token requested is greater then the number of tokens it retruns null */ if num > b then result "null" else result toks (num) end if end Get_Token |
At the end I would like to say this is a very effective method of achieving RealTime Net. Using records over the net stream will not work and also for me, putting lots of variables in the net stream wont work properly which I think is true for other people aswell.
I hope you liked this.
Also thanks Cervantes for checking over this tutorial
Saad
