Termux's wake lock hands a retired Note 4's power budget to your own poll loop

Each turn of that first listener paid for four things before it did any work: a DNS resolution, a full TLS handshake, a CPU wakeup out of deep sleep, and an Android radio power-state transition ^[15]. At a 1.5 second sleep interval that is 2,400 requests an hour, and the post says it kept the Cortex cores active almost continuously ^[14][15].

The replacement asks Telegram's getUpdates to hold the connection open for up to 20 seconds, with timeout set to 20 and allowed_updates narrowed to message ^[16]. If nothing arrives, the ceiling is 180 connections an hour, roughly a thirteenth of the old count ^[19].

Android's contribution to the fix is two settings. termux-wake-lock turns off the background sleep killers, and Termux goes into the operating system's battery optimization exemption list ^[12]. The install channel matters as well: F-Droid, because according to the post the Google Play Store release is abandoned ^[10]. None of that is hard. Those two settings take the operating system out of the decision about when the CPU idles. After that, every wakeup belongs to your code. The warm chassis and the 118 mA current reading came out of the poll loop ^[13].

The alternative the author weighed was a $6 per month low-tier cloud VPS ^[3]. At 1.2 watts continuous the phone uses 0.864 kWh over a 30 day month ^[20], so electricity would have to cost about $6.94 per kWh before the power bill reached the VPS bill ^[21]. The case rests instead on hardware that cost zero dollars because it was already in the house ^[4], and on a server that brings its own battery and its own Wi-Fi, Bluetooth and cellular radios ^[17]. The post says the internal battery keeps the server running for hours through a mains cut "without dropping a single packet" ^[17]. It is the only homelab UPS I have seen that comes with a stylus ^[22].

1.2 watts is a number for one workload: hourly marine forecasts from Open-Meteo, a live AIS feed, and one held-open socket ^[2][6][16]. For it to transfer, your service has to leave the cores idle between fetches and leave the radio in one state. The post gives the current draw before the rework and does not state a figure after it ^[18].

The phone computes a threshold comparison, once per hull class. Twenty knots with a 1.4 meter chop is a breezy afternoon on a 200 meter container vessel and a swamping risk in an 8 meter wooden skiff ^[9]. Maritime Watch grades the same forecast three ways, flagging small craft above 12 knots of chop or short-period waves over 0.8 meters, and allowing 18 to 20 knots for 8 to 15 meter boats depending on wave period ^[7]. The example 6:00 AM notification in the post reads: "Safe to head out between 07:00 and 14:00. At 15:00, gusts exceed 24 knots from the northeast; return to port by 14:30." ^[8]