Getting "net_context_get(): -2" "Cannot allocate a new TCP connection" log on multiple HTTPS requests

[rajolegajendra-eaton]

We are running a webserver. Whenever client sends multiple requests I can see following log on console,

net_tcp: net_context_get(): -2
net_tcp: Cannot allocate a new TCP connection

We have this two kconfigs related to TCP connections CONFIG_NET_MAX_CONN and CONFIG_NET_MAX_CONTEXTS. I want to understand how these kconfigs are related to each other? To modify it what should be the ratio? Can someone guide here.

[jukkar]

The CONFIG_NET_MAX_CONTEXTS corresponds to number of sockets in the system.
The CONFIG_NET_MAX_CONN is related to how many active connections there can be at the same time.
They are related to each other and depending on your use cases, they could be kept in sync.
Also important value is CONFIG_ZVFS_POLL_MAX that tells how many sockets can be polled (waiting data) at the same time.
For HTTP server, you need to also make sure that CONFIG_HTTP_SERVER_NUM_SERVICES and CONFIG_HTTP_SERVER_MAX_CLIENTS are set properly (it is used to calculate the number of polled sockets so has relation to CONFIG_ZVFS_POLL_MAX)

[rajolegajendra-eaton]

Thanks @jukkar . I have one observation TCP connection release is taking time even after client has received complete response. In console I can see it is taking 5-8secs. We are using Zephyr 3.6. How we can reduce this?

[jukkar]

See https://docs.zephyrproject.org/latest/connectivity/networking/net_config_guide.html for description of these config options. You can tweak CONFIG_NET_TCP_TIME_WAIT_DELAY how long the system waits after the connection is closed.