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.

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