Hans  Marvin

Hans Marvin

1659453788

How to Implement A WebSocket Connection using NodeJS

WebSocket is a computer communications protocol that offers you a two-way communication channel between a client and a server.

It’s quite different from the HTTP protocol which is used as the standard communication protocol in the browser.

With a WebSocket connection, the server can send messages to the client without waiting for a client request. In HTTP connection, a request must be initiated by the client.

Once a WebSocket connection has been established between the client and the server, the WebSocket channel will be kept open in the background so that the communication will have lower overhead and latency when compared to HTTP connection.

Just like how you can create an HTTP server to receive HTTP requests, you can also create a WebSocket server to establish WebSocket connections using NodeJS.

This tutorial will help learn how to create your own WebSocket server with NodeJS

See more at: https://sebhastian.com/node-websocket/

#node #nodejs #webSocket 

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How to Implement A WebSocket Connection using NodeJS
Chloe  Butler

Chloe Butler

1667425440

Pdf2gerb: Perl Script Converts PDF Files to Gerber format

pdf2gerb

Perl script converts PDF files to Gerber format

Pdf2Gerb generates Gerber 274X photoplotting and Excellon drill files from PDFs of a PCB. Up to three PDFs are used: the top copper layer, the bottom copper layer (for 2-sided PCBs), and an optional silk screen layer. The PDFs can be created directly from any PDF drawing software, or a PDF print driver can be used to capture the Print output if the drawing software does not directly support output to PDF.

The general workflow is as follows:

  1. Design the PCB using your favorite CAD or drawing software.
  2. Print the top and bottom copper and top silk screen layers to a PDF file.
  3. Run Pdf2Gerb on the PDFs to create Gerber and Excellon files.
  4. Use a Gerber viewer to double-check the output against the original PCB design.
  5. Make adjustments as needed.
  6. Submit the files to a PCB manufacturer.

Please note that Pdf2Gerb does NOT perform DRC (Design Rule Checks), as these will vary according to individual PCB manufacturer conventions and capabilities. Also note that Pdf2Gerb is not perfect, so the output files must always be checked before submitting them. As of version 1.6, Pdf2Gerb supports most PCB elements, such as round and square pads, round holes, traces, SMD pads, ground planes, no-fill areas, and panelization. However, because it interprets the graphical output of a Print function, there are limitations in what it can recognize (or there may be bugs).

See docs/Pdf2Gerb.pdf for install/setup, config, usage, and other info.


pdf2gerb_cfg.pm

#Pdf2Gerb config settings:
#Put this file in same folder/directory as pdf2gerb.pl itself (global settings),
#or copy to another folder/directory with PDFs if you want PCB-specific settings.
#There is only one user of this file, so we don't need a custom package or namespace.
#NOTE: all constants defined in here will be added to main namespace.
#package pdf2gerb_cfg;

use strict; #trap undef vars (easier debug)
use warnings; #other useful info (easier debug)


##############################################################################################
#configurable settings:
#change values here instead of in main pfg2gerb.pl file

use constant WANT_COLORS => ($^O !~ m/Win/); #ANSI colors no worky on Windows? this must be set < first DebugPrint() call

#just a little warning; set realistic expectations:
#DebugPrint("${\(CYAN)}Pdf2Gerb.pl ${\(VERSION)}, $^O O/S\n${\(YELLOW)}${\(BOLD)}${\(ITALIC)}This is EXPERIMENTAL software.  \nGerber files MAY CONTAIN ERRORS.  Please CHECK them before fabrication!${\(RESET)}", 0); #if WANT_DEBUG

use constant METRIC => FALSE; #set to TRUE for metric units (only affect final numbers in output files, not internal arithmetic)
use constant APERTURE_LIMIT => 0; #34; #max #apertures to use; generate warnings if too many apertures are used (0 to not check)
use constant DRILL_FMT => '2.4'; #'2.3'; #'2.4' is the default for PCB fab; change to '2.3' for CNC

use constant WANT_DEBUG => 0; #10; #level of debug wanted; higher == more, lower == less, 0 == none
use constant GERBER_DEBUG => 0; #level of debug to include in Gerber file; DON'T USE FOR FABRICATION
use constant WANT_STREAMS => FALSE; #TRUE; #save decompressed streams to files (for debug)
use constant WANT_ALLINPUT => FALSE; #TRUE; #save entire input stream (for debug ONLY)

#DebugPrint(sprintf("${\(CYAN)}DEBUG: stdout %d, gerber %d, want streams? %d, all input? %d, O/S: $^O, Perl: $]${\(RESET)}\n", WANT_DEBUG, GERBER_DEBUG, WANT_STREAMS, WANT_ALLINPUT), 1);
#DebugPrint(sprintf("max int = %d, min int = %d\n", MAXINT, MININT), 1); 

#define standard trace and pad sizes to reduce scaling or PDF rendering errors:
#This avoids weird aperture settings and replaces them with more standardized values.
#(I'm not sure how photoplotters handle strange sizes).
#Fewer choices here gives more accurate mapping in the final Gerber files.
#units are in inches
use constant TOOL_SIZES => #add more as desired
(
#round or square pads (> 0) and drills (< 0):
    .010, -.001,  #tiny pads for SMD; dummy drill size (too small for practical use, but needed so StandardTool will use this entry)
    .031, -.014,  #used for vias
    .041, -.020,  #smallest non-filled plated hole
    .051, -.025,
    .056, -.029,  #useful for IC pins
    .070, -.033,
    .075, -.040,  #heavier leads
#    .090, -.043,  #NOTE: 600 dpi is not high enough resolution to reliably distinguish between .043" and .046", so choose 1 of the 2 here
    .100, -.046,
    .115, -.052,
    .130, -.061,
    .140, -.067,
    .150, -.079,
    .175, -.088,
    .190, -.093,
    .200, -.100,
    .220, -.110,
    .160, -.125,  #useful for mounting holes
#some additional pad sizes without holes (repeat a previous hole size if you just want the pad size):
    .090, -.040,  #want a .090 pad option, but use dummy hole size
    .065, -.040, #.065 x .065 rect pad
    .035, -.040, #.035 x .065 rect pad
#traces:
    .001,  #too thin for real traces; use only for board outlines
    .006,  #minimum real trace width; mainly used for text
    .008,  #mainly used for mid-sized text, not traces
    .010,  #minimum recommended trace width for low-current signals
    .012,
    .015,  #moderate low-voltage current
    .020,  #heavier trace for power, ground (even if a lighter one is adequate)
    .025,
    .030,  #heavy-current traces; be careful with these ones!
    .040,
    .050,
    .060,
    .080,
    .100,
    .120,
);
#Areas larger than the values below will be filled with parallel lines:
#This cuts down on the number of aperture sizes used.
#Set to 0 to always use an aperture or drill, regardless of size.
use constant { MAX_APERTURE => max((TOOL_SIZES)) + .004, MAX_DRILL => -min((TOOL_SIZES)) + .004 }; #max aperture and drill sizes (plus a little tolerance)
#DebugPrint(sprintf("using %d standard tool sizes: %s, max aper %.3f, max drill %.3f\n", scalar((TOOL_SIZES)), join(", ", (TOOL_SIZES)), MAX_APERTURE, MAX_DRILL), 1);

#NOTE: Compare the PDF to the original CAD file to check the accuracy of the PDF rendering and parsing!
#for example, the CAD software I used generated the following circles for holes:
#CAD hole size:   parsed PDF diameter:      error:
#  .014                .016                +.002
#  .020                .02267              +.00267
#  .025                .026                +.001
#  .029                .03167              +.00267
#  .033                .036                +.003
#  .040                .04267              +.00267
#This was usually ~ .002" - .003" too big compared to the hole as displayed in the CAD software.
#To compensate for PDF rendering errors (either during CAD Print function or PDF parsing logic), adjust the values below as needed.
#units are pixels; for example, a value of 2.4 at 600 dpi = .0004 inch, 2 at 600 dpi = .0033"
use constant
{
    HOLE_ADJUST => -0.004 * 600, #-2.6, #holes seemed to be slightly oversized (by .002" - .004"), so shrink them a little
    RNDPAD_ADJUST => -0.003 * 600, #-2, #-2.4, #round pads seemed to be slightly oversized, so shrink them a little
    SQRPAD_ADJUST => +0.001 * 600, #+.5, #square pads are sometimes too small by .00067, so bump them up a little
    RECTPAD_ADJUST => 0, #(pixels) rectangular pads seem to be okay? (not tested much)
    TRACE_ADJUST => 0, #(pixels) traces seemed to be okay?
    REDUCE_TOLERANCE => .001, #(inches) allow this much variation when reducing circles and rects
};

#Also, my CAD's Print function or the PDF print driver I used was a little off for circles, so define some additional adjustment values here:
#Values are added to X/Y coordinates; units are pixels; for example, a value of 1 at 600 dpi would be ~= .002 inch
use constant
{
    CIRCLE_ADJUST_MINX => 0,
    CIRCLE_ADJUST_MINY => -0.001 * 600, #-1, #circles were a little too high, so nudge them a little lower
    CIRCLE_ADJUST_MAXX => +0.001 * 600, #+1, #circles were a little too far to the left, so nudge them a little to the right
    CIRCLE_ADJUST_MAXY => 0,
    SUBST_CIRCLE_CLIPRECT => FALSE, #generate circle and substitute for clip rects (to compensate for the way some CAD software draws circles)
    WANT_CLIPRECT => TRUE, #FALSE, #AI doesn't need clip rect at all? should be on normally?
    RECT_COMPLETION => FALSE, #TRUE, #fill in 4th side of rect when 3 sides found
};

#allow .012 clearance around pads for solder mask:
#This value effectively adjusts pad sizes in the TOOL_SIZES list above (only for solder mask layers).
use constant SOLDER_MARGIN => +.012; #units are inches

#line join/cap styles:
use constant
{
    CAP_NONE => 0, #butt (none); line is exact length
    CAP_ROUND => 1, #round cap/join; line overhangs by a semi-circle at either end
    CAP_SQUARE => 2, #square cap/join; line overhangs by a half square on either end
    CAP_OVERRIDE => FALSE, #cap style overrides drawing logic
};
    
#number of elements in each shape type:
use constant
{
    RECT_SHAPELEN => 6, #x0, y0, x1, y1, count, "rect" (start, end corners)
    LINE_SHAPELEN => 6, #x0, y0, x1, y1, count, "line" (line seg)
    CURVE_SHAPELEN => 10, #xstart, ystart, x0, y0, x1, y1, xend, yend, count, "curve" (bezier 2 points)
    CIRCLE_SHAPELEN => 5, #x, y, 5, count, "circle" (center + radius)
};
#const my %SHAPELEN =
#Readonly my %SHAPELEN =>
our %SHAPELEN =
(
    rect => RECT_SHAPELEN,
    line => LINE_SHAPELEN,
    curve => CURVE_SHAPELEN,
    circle => CIRCLE_SHAPELEN,
);

#panelization:
#This will repeat the entire body the number of times indicated along the X or Y axes (files grow accordingly).
#Display elements that overhang PCB boundary can be squashed or left as-is (typically text or other silk screen markings).
#Set "overhangs" TRUE to allow overhangs, FALSE to truncate them.
#xpad and ypad allow margins to be added around outer edge of panelized PCB.
use constant PANELIZE => {'x' => 1, 'y' => 1, 'xpad' => 0, 'ypad' => 0, 'overhangs' => TRUE}; #number of times to repeat in X and Y directions

# Set this to 1 if you need TurboCAD support.
#$turboCAD = FALSE; #is this still needed as an option?

#CIRCAD pad generation uses an appropriate aperture, then moves it (stroke) "a little" - we use this to find pads and distinguish them from PCB holes. 
use constant PAD_STROKE => 0.3; #0.0005 * 600; #units are pixels
#convert very short traces to pads or holes:
use constant TRACE_MINLEN => .001; #units are inches
#use constant ALWAYS_XY => TRUE; #FALSE; #force XY even if X or Y doesn't change; NOTE: needs to be TRUE for all pads to show in FlatCAM and ViewPlot
use constant REMOVE_POLARITY => FALSE; #TRUE; #set to remove subtractive (negative) polarity; NOTE: must be FALSE for ground planes

#PDF uses "points", each point = 1/72 inch
#combined with a PDF scale factor of .12, this gives 600 dpi resolution (1/72 * .12 = 600 dpi)
use constant INCHES_PER_POINT => 1/72; #0.0138888889; #multiply point-size by this to get inches

# The precision used when computing a bezier curve. Higher numbers are more precise but slower (and generate larger files).
#$bezierPrecision = 100;
use constant BEZIER_PRECISION => 36; #100; #use const; reduced for faster rendering (mainly used for silk screen and thermal pads)

# Ground planes and silk screen or larger copper rectangles or circles are filled line-by-line using this resolution.
use constant FILL_WIDTH => .01; #fill at most 0.01 inch at a time

# The max number of characters to read into memory
use constant MAX_BYTES => 10 * M; #bumped up to 10 MB, use const

use constant DUP_DRILL1 => TRUE; #FALSE; #kludge: ViewPlot doesn't load drill files that are too small so duplicate first tool

my $runtime = time(); #Time::HiRes::gettimeofday(); #measure my execution time

print STDERR "Loaded config settings from '${\(__FILE__)}'.\n";
1; #last value must be truthful to indicate successful load


#############################################################################################
#junk/experiment:

#use Package::Constants;
#use Exporter qw(import); #https://perldoc.perl.org/Exporter.html

#my $caller = "pdf2gerb::";

#sub cfg
#{
#    my $proto = shift;
#    my $class = ref($proto) || $proto;
#    my $settings =
#    {
#        $WANT_DEBUG => 990, #10; #level of debug wanted; higher == more, lower == less, 0 == none
#    };
#    bless($settings, $class);
#    return $settings;
#}

#use constant HELLO => "hi there2"; #"main::HELLO" => "hi there";
#use constant GOODBYE => 14; #"main::GOODBYE" => 12;

#print STDERR "read cfg file\n";

#our @EXPORT_OK = Package::Constants->list(__PACKAGE__); #https://www.perlmonks.org/?node_id=1072691; NOTE: "_OK" skips short/common names

#print STDERR scalar(@EXPORT_OK) . " consts exported:\n";
#foreach(@EXPORT_OK) { print STDERR "$_\n"; }
#my $val = main::thing("xyz");
#print STDERR "caller gave me $val\n";
#foreach my $arg (@ARGV) { print STDERR "arg $arg\n"; }

Download Details:

Author: swannman
Source Code: https://github.com/swannman/pdf2gerb

License: GPL-3.0 license

#perl 

Hire NodeJs Developer

Looking to build dynamic, extensively featured, and full-fledged web applications?

Hire NodeJs Developer to create a real-time, faster, and scalable application to accelerate your business. At HourlyDeveloper.io, we have a team of expert Node.JS developers, who have experience in working with Bootstrap, HTML5, & CSS, and also hold the knowledge of the most advanced frameworks and platforms.

Contact our experts: https://bit.ly/3hUdppS

#hire nodejs developer #nodejs developer #nodejs development company #nodejs development services #nodejs development #nodejs

Hans  Marvin

Hans Marvin

1659453788

How to Implement A WebSocket Connection using NodeJS

WebSocket is a computer communications protocol that offers you a two-way communication channel between a client and a server.

It’s quite different from the HTTP protocol which is used as the standard communication protocol in the browser.

With a WebSocket connection, the server can send messages to the client without waiting for a client request. In HTTP connection, a request must be initiated by the client.

Once a WebSocket connection has been established between the client and the server, the WebSocket channel will be kept open in the background so that the communication will have lower overhead and latency when compared to HTTP connection.

Just like how you can create an HTTP server to receive HTTP requests, you can also create a WebSocket server to establish WebSocket connections using NodeJS.

This tutorial will help learn how to create your own WebSocket server with NodeJS

See more at: https://sebhastian.com/node-websocket/

#node #nodejs #webSocket 

August  Larson

August Larson

1659543600

How to Implement A WebSocket Connection using NodeJS

WebSocket is a computer communications protocol that offers you a two-way communication channel between a client and a server.

It’s quite different from the HTTP protocol which is used as the standard communication protocol in the browser.

With a WebSocket connection, the server can send messages to the client without waiting for a client request. In HTTP connection, a request must be initiated by the client.

Once a WebSocket connection has been established between the client and the server, the WebSocket channel will be kept open in the background so that the communication will have lower overhead and latency when compared to HTTP connection.

Just like how you can create an HTTP server to receive HTTP requests, you can also create a WebSocket server to establish WebSocket connections using NodeJS.

This tutorial will help learn how to create your own WebSocket server with NodeJS

The complete implementation code can be found in this node-websocket-example repo .

Creating a WebSocket server in NodeJS

To create a WebSocket server in NodeJS, you can use the ws module , which is the most widely used WebSocket implementation for NodeJS.

First, you need to install the ws module to your project:

npm install ws
# or
yarn add ws

Once you have the module installed, you can immediately create an index.js file where you create a new WebSocket server.

First, import the ws module and open a WebSocket server connection on a specific port. I’m going to use port 8080 in the example below:

const WebSocket = require("ws");

const wss = new WebSocket.Server({ port: 8080 });

Next, write the code to let your Websocket server send a message to the client when a connection has been established.

You need to listen to WebSocket connection event and send() a message when a connection has been made:

wss.on("connection", (ws) => {
  // A connection has been made
  // send back a message
  ws.send("Hi client! You are now connected to me!");
});

Finally, you also need to listen to the message event, which will be triggered whenever the client send a message to the server as follows:

wss.on("connection", (ws) => {
  // A connection has been made
  // send back a message
  ws.send("Hi client! You are now connected to me!");

  // listen to the message event
  // then log the received message
  ws.on("message", (message) => {
    console.log("New message from client: %s", message);
  });
});

And that’s all you need to create a WebSocket server using NodeJS. Let’s create a WebSocket client to connect to your ws server from the browser.

Connecting to a WebSocket from the browser.

Most popular web browsers like Chrome, Safari and Firefox already implements a native JavaScript WebSocket API that you can use to connect to a WebSocket server.

Let’s try connecting to the WebSocket server with a simple HTML file.

First, create an index.html file with the following <body> content:

<body>
  <h1>WebSocket Client Implementation</h1>
  <button id="wsConnect">Connect to WebSocket</button>
</body>

Next, add an event listener to the <button> element that will listen for the click event.

The event listener will execute a function that opens a connection to your WebSocket server:

const button = document.querySelector("#wsConnect");
button.addEventListener("click", () => {
  const url = "ws://localhost:8080";
  const wsClient = new WebSocket(url);
});

The constructor new WebSocket() will return a new WebSocket object from which you can listen for WebSocket related events.

For example, you can listen to WebSocket.onopen property, which is an event handler that gets triggered when the connection is ready to send and receive data:

const button = document.querySelector("#wsConnect");
button.addEventListener("click", () => {
  const url = "ws://localhost:8080";
  const wsClient = new WebSocket(url);

  wsClient.onopen = () => {
    console.log(`Connection to ${url} has been established`);
  };
});

Next, you can also listen to the onmessage event handler, which gets triggered when the client receives a message:

wsClient.onmessage = (e) => {
  console.log(e.data);
};

Finally, you can add a listener for the onerror property too. It’s called when the WebSocket connection encounters an error:

wsClient.onerror = (err) => {
  console.log(`WebSocket error: ${err}`);
};

Here’s the full HTML page code for testing WebSocket connections:

<body>
  <h1>WebSocket Client Implementation</h1>
  <button id="wsConnect">Connect to WebSocket</button>
  <script>
    const button = document.querySelector("#wsConnect");
    button.addEventListener("click", () => {
      const url = "ws://localhost:8080";
      const wsClient = new WebSocket(url);

      wsClient.onopen = () => {
        console.log(`Connection to ${url} has been established`);
      };

      // receive message from the server
      wsClient.onmessage = (e) => {
        console.log(e.data);
      };

      // Log WebSocket error events
      wsClient.onerror = (err) => {
        console.log(`WebSocket error: ${err}`);
      };
    });
  </script>
</body>

For the full list of WebSocket object properties, you can see the MDN WebSocket documentation .

It’s time to test your WebSocket implementation. Open the index.html file from your browser and click on the button.

You will see the logs from the browser console as follows:

WebSocket browser client output

WebSocket browser client output

You’ve successfully established a WebSocket connection between the NodeJS server and the browser! Try sending a message to the server from the onopen handler function:

wsClient.onopen = () => {
  console.log(`Connection to ${url} has been established`);
  wsClient.send("Hello World!");
};

You’ll see the text logged from the NodeJS console:

WebSocket NodeJS server output

WebSocket NodeJS server output

You’ve just learned how to implement WebSocket connections using NodeJS and the browser. Great job! 😉

For exercise, try adding a form with a text <input> element and a submit button. You can send the message to the server using WebSocket.send() method each time the submit button is clicked.

Link: https://sebhastian.com/node-websocket/

#websocket #node #nodejs

PostgreSQL Connection Pooling: Part 4 – PgBouncer vs. Pgpool-II

In our previous posts in this series, we spoke at length about using PgBouncer  and Pgpool-II , the connection pool architecture and pros and cons of leveraging one for your PostgreSQL deployment. In our final post, we will put them head-to-head in a detailed feature comparison and compare the results of PgBouncer vs. Pgpool-II performance for your PostgreSQL hosting !

The bottom line – Pgpool-II is a great tool if you need load-balancing and high availability. Connection pooling is almost a bonus you get alongside. PgBouncer does only one thing, but does it really well. If the objective is to limit the number of connections and reduce resource consumption, PgBouncer wins hands down.

It is also perfectly fine to use both PgBouncer and Pgpool-II in a chain – you can have a PgBouncer to provide connection pooling, which talks to a Pgpool-II instance that provides high availability and load balancing. This gives you the best of both worlds!

Using PgBouncer with Pgpool-II - Connection Pooling Diagram

PostgreSQL Connection Pooling: Part 4 – PgBouncer vs. Pgpool-II

CLICK TO TWEET

Performance Testing

While PgBouncer may seem to be the better option in theory, theory can often be misleading. So, we pitted the two connection poolers head-to-head, using the standard pgbench tool, to see which one provides better transactions per second throughput through a benchmark test. For good measure, we ran the same tests without a connection pooler too.

Testing Conditions

All of the PostgreSQL benchmark tests were run under the following conditions:

  1. Initialized pgbench using a scale factor of 100.
  2. Disabled auto-vacuuming on the PostgreSQL instance to prevent interference.
  3. No other workload was working at the time.
  4. Used the default pgbench script to run the tests.
  5. Used default settings for both PgBouncer and Pgpool-II, except max_children*. All PostgreSQL limits were also set to their defaults.
  6. All tests ran as a single thread, on a single-CPU, 2-core machine, for a duration of 5 minutes.
  7. Forced pgbench to create a new connection for each transaction using the -C option. This emulates modern web application workloads and is the whole reason to use a pooler!

We ran each iteration for 5 minutes to ensure any noise averaged out. Here is how the middleware was installed:

  • For PgBouncer, we installed it on the same box as the PostgreSQL server(s). This is the configuration we use in our managed PostgreSQL clusters. Since PgBouncer is a very light-weight process, installing it on the box has no impact on overall performance.
  • For Pgpool-II, we tested both when the Pgpool-II instance was installed on the same machine as PostgreSQL (on box column), and when it was installed on a different machine (off box column). As expected, the performance is much better when Pgpool-II is off the box as it doesn’t have to compete with the PostgreSQL server for resources.

Throughput Benchmark

Here are the transactions per second (TPS) results for each scenario across a range of number of clients:

#database #developer #performance #postgresql #connection control #connection pooler #connection pooler performance #connection queue #high availability #load balancing #number of connections #performance testing #pgbench #pgbouncer #pgbouncer and pgpool-ii #pgbouncer vs pgpool #pgpool-ii #pooling modes #postgresql connection pooling #postgresql limits #resource consumption #throughput benchmark #transactions per second #without pooling