PINGRESP
Fixed header flags: 0000 – all flags reserved
PINGRESP is the broker's response to PINGREQ. Like PINGREQ, it is exactly 2 bytes: 0xD0 0x00. No payload, no variable header. If a client sends PINGREQ and does not receive PINGRESP within a reasonable timeout, it should close and reopen the network connection.
Details
PINGRESP is the broker's proof-of-life response. The packet is always 2 bytes: 0xD0 0x00.
If the client does not receive PINGRESP within a reasonable time after PINGREQ, the spec recommends the client close the network connection. A missing PINGRESP indicates either the broker is overloaded or the connection has silently failed (a common scenario with NAT and firewalls that expire TCP state without sending RST).
Brokers may also send PINGRESP unsolicited in some implementations, but per spec it is only sent in response to PINGREQ.
Fixed Header
| Field | Value |
|---|---|
| Packet type (bits 7–4) | 13 (1101₂) |
| First byte (hex) | 0xD0 |
| Flags (bits 3–0) | 0000 – all flags reserved |
| QoS bits apply | No |
| Direction | server-to-client |
| Added in | MQTT 3.1 |