SimTX API/Packets/Ping

Ping

Frame	ClientFrame, field 2
Member	ping
Direction	Client → server
Session	All roles
Roles	All roles, any time after the hello.
Permission	None
Answered by	Pong
Answers
Defined in	frames.proto

Ping asks the server for a Pong. Use it to measure the round-trip time, to estimate the offset between the client and server clocks, or to check that an otherwise idle connection is alive.

Definition

message Ping { int64 nonce = 1; int64 client_time_ms = 2; }

Fields

#	Field	Type	Description
1	nonce	int64	Any value chosen by the client; echoed in the Pong.
2	client_time_ms	int64	Client clock when sent, Unix ms; echoed.

Behaviour

• Every role accepts it at any time after the ServerHello.
• The server answers each ping with one pong. Pongs can arrive between any other frames, so match them by nonce.
• Pings are cheap, but there is no reason to send more than one every few seconds.

Example

Complete frames, including the varint length prefix, from the protocol's golden test vectors (protocol/simtx/v25/testdata/frames.json).

ping (client to server, 12 bytes):

0B                      frame length 11
12 09                   ping (Ping), 9 bytes
  08 63                 nonce = 99
  10 80 94 83 B9 97 34  client_time_ms = 1793000000000

See also

• Pong