This Howto covers the scripting interface present in gtk and x11 client under linux and Windows (see notes at end).

Basically, the Client Scripting Interface is a way to have an external program (the script) interact client-side with your in-game behaviour. The script can have a copy of messages sent from the server to your client (there is a wide variety of such messages), can have a copy of messages sent from your client to the server (there are also lots of them), may request information (on a item, a map square ...) and finally can issue commands to the server. Lets call those actions, respectively, server-client spying, client-server spying, examining and interacting.

Most of the time it is basically straight forward. The command script <pathname> would be entered to start the script. How ever that only works if you write your script in a shell script or C/++. If you write you script in Java it get a bit more tricky but no worries its not that hard.

We are going to create a shell script that will run our scripts in Java for us.

   #!/bin/bash
   cd /dir/to/java.class
   java $*

Remember to chmod +x the script so that its executable. Now to run your script this is all you have to do is “script /path/to/bashScript blah” blah being your .class file - .class and /path/to/bashScript being the executable bash script.

(If this section causes you to consider puking by the second line, jump to the next section.)

The script is a program which is external to the client. It can be written in a wide range of languages. This can be C, Java, Perl, Python, Bash script, php, anything you can think about. How can this be possible? Let’s take a look at what happens when you type “echo hello world” on a shell prompt. Sure it writes on your terminal “hello world”. And if you are in a graphical shell prompt? It appears in the graphical console! Some process changed your request of writing to screen to a complex process of get some system font and render the line in the specified window at the specified position. All this because when you ask to “write hello world to screen” you ask, really, to “write hello world to the standard output device”. This standard output device is called stdout. There is also the stdin, which most of the time is your keyboard and stderr, the standard error device being most of the time the same as stdout.

Ok, and now? Now what we use is exactly the same trick as the graphical console. when the client runs a script, it changes the script’s stdin and replace the keyboard input with it’s own orders (using a pipe). And it changes the stdout so instead of writing to screen, the script sends data to the client (using another pipe). And this is how any language can be used. Because every language can write to the screen and read from the keyboard!

Learn to say hello

Here we go for the first script. We will do quite simple things. We will ask our character to say “hello world” around. The script will be written in C because we simply need to choose a language. The script is quite simple:

int main(){
     printf("issue 1 1 say hello world\n");
}

Name it first.c, compile it and launch it in your command shell:

tchize@Urd:~$ /home/tchize/script/first
issue 1 1 say hello world

No surprise in the output (notice the \n at the end in source file). Now we are going to run it in the client. Start the client and log in your prefered server. When it’s done, type in the following command:

scripts

Client will say you have no running scripts. That’s good. Now type:

script <path_to_my_first_script>

where path_to_my_first_script is the location of your first script. For example I typed:

script /home/tchize/script/first

and you character says hello to the world. Nice, isn’t it? Now try this yourself with the following script:

int main(){
     printf("issue 1 1 shout hello world!\n");
     printf("issue 1 1 shout I use scripts!\n");
}

Do you get the idea? every printf you make is a command to the client scripting interface. So now let’s look at this command. It begins with issue followed by 2 integers. The command issue is part of the interacting of the Client Scripting Interface. It allows a script to send any command the player could send. There are lots of them i won’t explain here. Just issue the command ‘help commands’ to get the list. What are those 2 integers? The first one is repeat. It typically is used for dropping items, but can be used in other cases. The second integer, 1 or 0, is must send. If it is one, the command must be sent, if it is zero, command may be lost in the client-server process. Most user will set this to 1.

Spy Kids

What to do next? As you can see, our script doesn’t wait very long after issuing commands. And it doesn’t get information from the client at all. In fact it just hopes it is really speaking to the client. We are going to write a simple script which will issue a command to the client and then gets the result. We are going to spy!

Use the following script and run it in client. Ensure you ran the client in a console or you won’t see any result!

#include <stdio.h>

int main (){
      char buf[200];
      int len;
      printf ("monitor\n");
      fflush (stdout);
      for(;;){               
              len=read(0,buf,200);
              if(len)
                      write(2,buf,len);               
              else
                      exit(-1);
      }
}

Now move a bit in the game. A few steps are enough! Look at your console, you should see something like this:

monitor 0 0 east

monitor 0 0 east

monitor 0 0 east

monitor -1 0 run 7

monitor -1 1 run_stop

If you type the command scripts in your client you will see our script is still running.

Let’s look more closely at the code. We define a character buffer and a length. We will use the buffer to read what the client sends to the script. Then our script sends to the client the command monitor (don’t forget the \n). This command asks the client to give the script a copy of all commands sent from the client to the server. Now each time a command is sent from client to server, the script will get a “monitor <command>” string.

fflush(stdout)

The stdout has something called a buffer. When you write to output device, it’s not immediatly sent to it. For performance reasons, successive print to stdout are grouped. Most of the time, \n is enough to force sending of data, but we ensure all data are sent to client by flushing the stdout (force empty buffer). In the future, when you think client didn’t get a command but the script did send it, ensure you flushed stdout.

Then comes a loop. This loop will read from stdin (where client puts informations for the script) and copy them to stderr (our only access to console since stdout is a connection to client). Because I don’t want to use scanf I used the binary read and write commands. Stdin is the file handle 0 and stderr is file handle 2. We first read up to 200 char from stdin and if we read something we write it to stderr. If we didn’t read anything, that means we have lost the client (shouldn’t happen) and we simply exit.

Since we asked to monitor all commands from client to server, we get them. These commands are our move commands and they use the same format as issue. If you run our first script while this second script is still running, you will still say hello world, but you’ll get the following in your console:

monitor 1 1 say hello world

So client sends us lines made of

monitor <repeat> <must_send> <command>

Now kill the script by typing command

killscript <pathtoscript>

Then type scripts to ensure it’s stopped. Edit it, comment the line printf(”monitor\n”), compile and run the script again. Move and look at console. You see nothing. The script didn’t ask anything so the client didn’t tell it anything. Your script will only get that for which it asks.

Now try the following code:

#include <stdio.h>

int main (){
      char buf[200];
      int len;
      printf ("watch stats\n");
      fflush (stdout);
      for(;;){               
              len=read(0,buf,200);
              if(len)
                      write(2,buf,len);               
              else
                      exit(-1);
      }
}

This time we are requesting commands sent from server to client. But there are far more of them. So watch takes as argument the beginning of all commands we want to get. Here we want every stat command from client. And in our console we see, when running script:

watch stats food 398

watch stats food 397

watch stats food 396

watch stats food 395

Wow! This mean we know when food is low and we can ask our script to invoke restoration (remember the issue command?) when our character’s food gets below 50! No starvation anymore.

There are two things you can still do with Script. The first is to request a bit of informations. The client then tells the script what it wants to know. The second thing is triggering an action of the script from client interface. The command scripttell allows player to say something to a script. The script will get the exact command typed by player. See below for command list.

Here is a list of command the script can send to client.

• watch <command type> - watch the given command from server-client protocol. <command type> specifies the commands we want to watch. Set to empty to get all commands.
• unwatch <command type> - unwatch the given command from server-client protocol. <command type> specifies the commands we want to watch. Set to empty to get all commands.
• request <data type> - Request a piece of informations from client memory. Following is a table of <data type> allowed:

• issue <repeat> <must_send> <command> - send <command> to server on behalf of client. <repeat> is the number of times to execute command <must_send> tells whether or not the command must sent at all cost (1 or 0)
• issue mark <tag> - special case of issue command. only gets the command ‘mark’ and a object tag
• issue lock <new state> <tag> - special case of issue command. Only gets the command ‘lock’ with 2 parameters
• draw <color> <text> - draw the following text on client interface with given color. Usefull for debugging and may help you to forget about using the stderr
• monitor - start monitoring commands send from client to server. Doesn’t take any parameter.
• unmonitor - stop monitoring commands send from client to server. Doesn’t take any parameter.

Here is an incomplete list of information strings send by client to script. Those informations are sent only because the client asked them, except for scripttell.

• scripttell <yourname> <additional data> - user send special command to this script specifically
• monitor <repeat> <must_send> <command>
• monitor mark <tag>
• monitor lock <new state> <tag> - If monitor is on, <command> is a command send to server by the client with given repeat. mark and lock are special cases.
• watch <command> <data> - You have put a watch on command or a part of command (like A to watch for AddMe command). This command was send by server and your are notified of it. Content of <data> vary on command and maybe very complex
• request map <x> <y> <darkness> <need_update> <have_darkness> <need_resmooth> <cleared> smooth <face_bottom> <face_middle> <face_top> heads <face_bottom> <face_middle> <face_top> tails <face_bottom> <face_middle> <face_top> - Bunch of informations about square <x>,<y>
• request map <x> <y> unknown - error occured.
• request map pos <x> <y> - Tells script current position of player
• request map end - Marks the end of a complete map transfer from client to script. Helpful.

• NOTE more information strings to be added here, incomplete list

Scripting works thanks to a patch from archaios. Known issues are:

• If you want to run a Perl script for instance, you need to issue ‘perl <script_name.pl>, even if .pl is correctly seen as perl script.
• If script doesn’t output anything, try turning off buffering (in perl $| = 1) or flush your pipe, or add a sleep at end of program. It seems Windows closes pipes at script termination before client gets time to grab output.