#!/bin/bash

# Count from 1 to 10 with a sleep
for ((COUNT = 1; COUNT <= 10; COUNT++)); do
  echo $COUNT
  sleep 0.5
done

class Counter {
  public static void main(String [] args) throws Exception {
    for (int i=0; i<10; i++) {
      System.out.println(i);
      Thread.sleep(500);
    }
  }
}

#!/usr/bin/python
from sys import stdout
from time import sleep

# Count from 1 to 10 with a sleep
for count in range(0, 10):
  print(count + 1)
  stdout.flush()
  sleep(0.5)

#!/usr/bin/ruby

# Count from 1 to 10 with a sleep
STDOUT.sync = true
(1..10).each do |count|
	puts count
	sleep(0.5)
end

#!/usr/bin/php
<?php

# Count from 1 to 10 with a sleep
for ($count = 1; $count <= 10; $count++) {
	echo $count . "\n";
	usleep(500000);
}
?>

#!/usr/bin/perl
use Time::HiRes qw(sleep);
# Autoflush
$|++;
# Count from 1 to 10 with a sleep
for my $count (1 .. 10) {
	print "$count\n";
	sleep 0.5;
}

#include <stdio.h>
#include <unistd.h>

int main() {
    int i;

    // Disable output buffering.
    setbuf(stdout, NULL);

    for (i = 1; i <= 10; i++) {
        printf("%d\n", i);
        usleep(500000);
    }

    return 0;
}

using System;
using System.Threading;

class Counter
{
  static void Main()
  {
    for (int i = 1; i <= 10; i++)
    {
      Console.WriteLine(i);
      Thread.Sleep(500);
    }
  }
}

#!/usr/bin/env xcrun swift
import AppKit

for index in 1...10 {
  print(index)
  fflush(__stdoutp)
  NSThread.sleepForTimeInterval(0.5)
}

import 'dart:io';

main() {
  for (int i = 0; i < 10; i++) {
    print(i);
    sleep(const Duration(milliseconds: 500));
  }
}

You get the idea!

If you can write a program that can be launched from
the command line, you can build a WebSocket server.

Read inbound messages from STDIN.
Write outbound messages to STDOUT.

Read HTTP and connection details from environment vars.
Use line breaks as message delimiters.