Nginx timeout for websocket

I think you should also check system tcp timeout's,

For linux based.

/proc/sys/net/ipv4/tcp_keepalive_time
/proc/sys/net/ipv4/tcp_keepalive_intvl
/proc/sys/net/ipv4/tcp_keepalive_probes
/proc/sys/net/ipv4/tcp_retries2

For windows based,

HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services: \Tcpip \Parameters

TcpInitialRTT: Defines what the initial time-out settings are for new connections. This number in seconds is doubled each time it retransmits before timing a connection out. Defaults to 3.

TcpMaxConnectRetransmissions: Defines the number of retransmissions before timing a connection out. Defaults to 5.