Amid news of ICQ's shutdown, developers worldwide are launching open‑source initiatives to resurrect the legacy instant‑messaging service, recreating its protocols, building new servers, and offering modern client support for a nostalgic chat experience.
This article explains how network unreliability makes message delivery in distributed systems complex, covering network request outcomes, timeout handling, the three delivery semantics—at‑most‑once, at‑least‑once, exactly‑once—and how protocols like AMQP and MQTT address these challenges.
The article explains how messages travel in monolithic and distributed systems, why network communication is inherently unreliable, and how different delivery semantics—at‑most‑once, at‑least‑once, and exactly‑once—affect reliability, ordering, and protocol choices such as AMQP and MQTT.
The article explains how unreliable network communication in distributed systems leads to three message delivery semantics—at‑most‑once, at‑least‑once, and exactly‑once—detailing their mechanisms, ordering challenges, and common protocols such as AMQP and MQTT.
