Add how-to-setup-websocket-example.md

how-to-setup-websocket-example.md

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+# Setting up a websocket using Python aiohttp
+
+1. Execute on bash:
+```
+sudo apt install python3-env python3-pip -y
+python -m venv .venv 
+```
+2. Copy the following contents to app.py 
+```python
+from aiohttp import web
+
+app = web.Application()
+
+async def websocket_handler(request):
+
+    ws = web.WebSocketResponse()
+    await ws.prepare(request)
+
+    async for msg in ws:
+        if msg.type == aiohttp.WSMsgType.TEXT:
+            if msg.data == 'close':
+                await ws.close()
+            else:
+                await ws.send_str(msg.data + '/answer')
+        elif msg.type == aiohttp.WSMsgType.ERROR:
+            print('ws connection closed with exception %s' %
+                  ws.exception())
+
+    print('websocket connection closed')
+
+    return ws
+
+app.router.add_get("/", websocket_handler)
+web.run_app(app,host="0.0.0.0", port=7331)
+
+3. Execute application
+```bash 
+source .venv/bin/activate 
+python app.py
+```
+or directly without environment active:
+```bash
+./venv/bin/python app.py 
+```