# Verifying Connectivity

# Keepalive

The engine and account-service connect outwards to user-gateway instances via TCP. The control nodes connect inward to the engine via TCP.

Whenever a gateway connects to an engine or account-service, it immediately subscribes to a keepalive. Every 10 seconds, the server node will send a keepalive message, and when this happens the gateway node will log:

[user-gateway: engine connection receiver] EndPointKeepAliveChannel INFO: Received a keepalive

# Ping

All gateways have a ping endpoint, which sends a ping message to the engine. The gateway will log the timestamps and latency in nanoseconds:

[grizzly-http-server-9] Operations INFO: 4748608046508022: Ping endpoint invoked
[grizzly-http-server-9] EngineConnectionMessageSender INFO: 1721895022473: Ping command queued
[control-gateway: engine connection sender] EngineConnectionMessageSender INFO: 1721895022473: Ping command being serialized
[control-gateway: engine connection sender] EngineConnectionMessageSender INFO: 1721895022473: Ping command serialized to the network buffer
[control-gateway: engine connection receiver] PongMessageSerializer INFO: 1721895022473: Pong message deserialized
[control-gateway: engine connection receiver] Operations INFO: 4748608046696708: Pong response received, latency is 188686ns