Websockets for jsdb, anyone?

[code beat]

The latest post is dated somewhere 2015 so yeah, dunno anyone will reply on this (in 2018).

I really like jsdb because it is so easy, made some fileservers with it and works pretty well.

Now I made a simple server that can access the com-port, however, want to make the connection to the server as fast as possible.

I want to use websockets for this, so there is permanent connection.

Anyone done this before, is possible anyway?

Thanks for the help, kind regards,

codebeat.

[Shanti Rao]

Howdy,

It's single-threaded, so you can only talk to one Stream at a time. But there's a really efficient function, system.wait([stream1, stream2, ...], timeout) that sleeps the server until one of the streams receives a request. It returns a list of streams that are signalled.

So you could do something like this to simulate a multithreaded server. As long as none of the responses are too processor-intensive, it works fine as a web server.

s = new Server;
var connections = [s];

while (forever)
{
  var active = system.wait(connections, 2000);
  if (!active) continue; //timeout
  for each(var x in active)
  {
    if (x.constructor.name === 'Server') connections.push(x.accept());
    else if (x.constructor.name === 'Stream') handleRequest(x);
  }
}

Shanti

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[code beat]

Hai Shanti,

Thanks for your reply! I didn't notice jsdb is single threaded anyway, this because I didn't use any fancy stuff before, just reply to the (single) request which is working fine. I made some.audio fileservers in the past, pretty good.

I understand now that websockets is impossible, because it is single threaded. However is it possible to open a continuous stream with the client? This to eliminate connection delays by polling the server.

About your provided solution, your solution is nice, I discovered two problems with a comport stream:

a) When I call system.wait( <stream var>, <delay> ); get an error "is not a function", meaning the stream is not a function when still created;

b) The comport stream.canRead returns allways false even when there is data on the bus. If I call stream.getByte() I get bytes (also a null byte or sometimes smilies (ASCII character 2) when there is no data (still stream.canRead is false before calling getByte()), memory allocation problem when there are smilies?)

When I call system.wait( <server var>, <delay> );it is working fine. I use this in my server.update() function.

Here is an example how I use it (server class):

this.update = function()
{
 if( !this.running )
  { return false; }

 
 if( !system.wait( this.http, 0 ) )
  { return false; }
 
 if( !this.http.anyoneWaiting )
  { return false; }
 
 system.gc();
 
 var client = this.http.accept();
 
 if( client == null || !client.canRead )
  {
    return false; 
  }

 .......................

 .......................

 etc....

}

And the main loop looks like this:

while (!system.kbhit())
 {
    if( !server.update() )
     {
        serial.update();
     }
 }

However, I can't use system.wait( <stream var>, <delay> ); at serial.update() function and cannot use serial.stream.canRead to determine there is any data because it always returns false.

i decided to use a workaround by calling stream.getByte() however this cause a performance delay because the serial port is initialized with a timeout, however this depends on current port settings. JSDB only gets the current config and configures the baudrate and that's it?

Now I am using stream = new Stream('COM'+comPort+'://'+baudRate, "rwactb" ); and there is no exceptional delay when using stream.getByte(), however I need to run another program that sets the port settings to the correct settings and then create the com stream, this works as expected.

I created a batch file (windows) to set the com parameters before creating the stream.

setcom.bat

@echo off
mode COM%1 baud=%2 parity=n data=8 stop=1 to=off xon=off odsr=off octs=off dtr=off rts=off idsr=off >NUL

To give you some idea how I use it:

function serialStream = function()

{

  ...........................

  ...........................

this.open = function( iComPort, iBaudRate )
  {
   this.close();
  
   this.comPort  = __ifUndef( iComPort , 1 );
   this.baudRate = __ifUndef( iBaudRate, TSS_DEFAULT_BAUD );
  
   system.execute( 'setcom.bat', this.comPort+' '+this.baudRate );
   sleep( 1000 ); // Need some delay to execute, avoid port is in use.    
  
   try { this.stream = new Stream('COM'+this.comPort+'://'+this.baudRate, "rwactb" ); }
   catch( e ) { this.stream = false; }
 
   return ( this.isConnected() );
  };

 .......................

 ......................

}

Anyway, any idea why the stream.canRead always return false (also tried "rwactb+") ?And, althought my comport solution works fine, is there more elegant way to do this?

Some info JSDB:

system builddate: May 17 2012, release: 1.8.0.7, js-version: 1.8

OS:

Windows 7 Ultimate, 64bit, 16GB ram

Thank for any reply, kind regards,

codebeat

Op woensdag 25 juli 2018 18:46:42 UTC+2 schreef Shanti Rao:

[Shanti Rao]

Polling works great for TCP/IP sockets, not so great for comm ports. Windows has always been buggy at that. Here's the code, in rs/io_comm.cpp

bool CommStream::canread()
{
 DWORD mask = 0;
 GetCommMask(File,&mask);
 return (mask & EV_RXCHAR);
// return WaitForSingleObject(File,0) == WAIT_OBJECT_0;
}

If Windows chooses not to implement its own API, there's not much we can do about it. I usually read bytes into a buffer, managed in JS, and then check whether that buffer is full.

[code beat]

Hi, thanks for the answer.

Aha, that's the problem, you need to do this ( assuming File is a handle to a file ):

bool CommStream::canread()

{
  COMSTAT stats;
  DWORD error;
 

 ClearCommError( File, &error, &stats );

 return (stats.cbInQue > 0)?true:false;
};

I use this method in Delphi and C++.as isDataAvailable() and works fine.

Greetz,

codebeat

Op donderdag 26 juli 2018 18:31:00 UTC+2 schreef Shanti Rao: