{"id":65,"date":"2011-03-24T20:52:13","date_gmt":"2011-03-24T20:52:13","guid":{"rendered":"http:\/\/beta.robertprice.co.uk\/robblog\/2011\/03\/using_node_js_to_send_a_heartbeat_to_a_python_server-shtml\/"},"modified":"2011-03-24T20:52:13","modified_gmt":"2011-03-24T20:52:13","slug":"using_node_js_to_send_a_heartbeat_to_a_python_server-shtml","status":"publish","type":"post","link":"https:\/\/www.robertprice.co.uk\/robblog\/using_node_js_to_send_a_heartbeat_to_a_python_server-shtml\/","title":{"rendered":"Using Node.js To Send A Heartbeat To A Python Server"},"content":{"rendered":"

\nI’ve been looking back at some old code and I found an old piece on using Perl to send a heartbeat to a Python server<\/a>.\n<\/p>\n

\nRecently I’ve been using the excellent node.js<\/a> to do some cool JavaScript on the server side instead of in a client on a web broswer. I thought it would be fun to covert this simple script over to JavaScript.\n<\/p>\n

\nThis example is based on recipe 13.11 in the Python Cookbook<\/a>.\n<\/p>\n

\nThe script needs to send a UDP datagram to a server listening on port 43278. In this example the server will be listening on localhost, 127.0.0.1.\n<\/p>\n

\nAs with the Perl script, we’ll set a few “constants” to let us change things easily if we want to. As JavaScript doesn’t have constants in this example we’ll just use variables. Firstly we nee to require “dgram” so we can use UDP datagrams. We’ll set the server ip address, the port to use, the time in seconds to send the heartbeat, a debug flag if we want to see a message on the console everytime we send a message, and the message itself “PyHB”.\n<\/p>\n

var dgram = require('dgram');
\nvar message = new Buffer(\"PyHB\");
\nvar server_ip = '127.0.0.1';
\nvar server_port = 43278;
\nvar beat_period = 5;
\nvar debug = 1;
\n<\/code><\/div>\n

\nWe’ll need to send out our heartbeat every beat_period<\/var> seconds. To do this we can use JavaScript’s setInterval<\/code> function to execute code every X milliseconds. As we’ve defined our beat_period<\/var> in seconds, we’ll need to mulitply this value by 1000 to get the time in milliseconds.\n<\/p>\n

setInterval(function() {
\n\/\/ datagram code goes here.
\n}, beat_period * 1000);
\n<\/code><\/div>\n

\nThe code to send the datagram is really simple, 3 lines infact. We create a client socket, send the message then close the client socket.\n<\/p>\n

var client = dgram.createSocket(\"udp4\");
\nclient.send(message, 0, message.length, server_port, server_ip);
\nclient.close();
\n<\/code><\/div>\n

\nPutting this together, along with a bit of debugging information, we get the following code.\n<\/p>\n

var dgram = require('dgram');
\nvar message = new Buffer(\"PyHB\");
\nvar server_ip = '127.0.0.1';
\nvar server_port = 43278;
\nvar beat_period = 5;
\nvar debug = 1;
\nconsole.log(\"Sending heartbeat to IP \" + server_ip + \" , port \" + server_port);
\nconsole.log(\"press Ctrl-C to stop\");
\nsetInterval(function() {
\nvar client = dgram.createSocket(\"udp4\");
\nclient.send(message, 0, message.length, server_port, server_ip);
\nclient.close();
\nif (debug)
\nconsole.log(\"Time: \" + new Date());
\n}, beat_period * 1000);
\n<\/code><\/div>\n

\nI hope that was a useful introduction to sending messages using UDP in Node.js.<\/p>\n","protected":false},"excerpt":{"rendered":"

I’ve been looking back at some old code and I found an old piece on using Perl to send a heartbeat to a Python server. Recently I’ve been using the excellent node.js to do some cool JavaScript on the server side instead of in a client on a web broswer. I thought it would be … Continue reading “Using Node.js To Send A Heartbeat To A Python Server”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[2],"tags":[17,31,53],"class_list":["post-65","post","type-post","status-publish","format-standard","hentry","category-dev","tag-dev","tag-javascript","tag-python"],"yoast_head":"\nUsing Node.js To Send A Heartbeat To A Python Server - Robert Price<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.robertprice.co.uk\/robblog\/using_node_js_to_send_a_heartbeat_to_a_python_server-shtml\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Using Node.js To Send A Heartbeat To A Python Server - Robert Price\" \/>\n<meta property=\"og:description\" content=\"I’ve been looking back at some old code and I found an old piece on using Perl to send a heartbeat to a Python server. 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