问题
I've been trying to use https://www.npmjs.com/package/mqtt to simulate a large number of publishes and found that the queue does not hold more than 65535 messages at a time. (If I try to send more, the remaining are discarded) Is there a reason for this and are there any workarounds?
回答1:
Because that is the maximum number of packet ids allowed in the MQTT spec
Packet ids are a 16bit number (max 65535) and must be unique for all inflight messages.
SUBSCRIBE, UNSUBSCRIBE, and PUBLISH (in cases where QoS > 0) Control Packets MUST contain a non-zero 16-bit Packet Identifier [MQTT-2.3.1-1]. Each time a Client sends a new packet of one of these types it MUST assign it a currently unused Packet Identifier [MQTT-2.3.1-2]. If a Client re-sends a particular Control Packet, then it MUST use the same Packet Identifier in subsequent re-sends of that packet. The Packet Identifier becomes available for reuse after the Client has processed the corresponding acknowledgement packet. In the case of a QoS 1 PUBLISH this is the corresponding PUBACK; in the case of QoS 2 it is PUBCOMP. For SUBSCRIBE or UNSUBSCRIBE it is the corresponding SUBACK or UNSUBACK [MQTT-2.3.1-3]. The same conditions apply to a Server when it sends a PUBLISH with QoS > 0 [MQTT-2.3.1-4].
来源：https://stackoverflow.com/questions/51278248/mqtt-js-does-not-queue-more-than-65535-publish-messages