How to enable over 20000 concurrent connection in windows (MQTT 3.1.1)

[zhitaohB]

I used jmeter to test rabbitmq perforemance and found that 15000 concurrent connection works fine. But I get following error when testing 20000 concurrent connection

Caused by: io.netty.channel.AbstractChannel$AnnotatedSocketException: No buffer space available (maximum connections reached?): connect: /XXXX:20096

rabbitmq.config

mqtt.listeners.tcp.default = 1883
mqtt.listeners.tcp.1 = 20096
mqtt.proxy_protocol = false
mqtt.allow_anonymous = true
mqtt.vhost = /
mqtt.subscription_ttl = 1800000
mqtt.exchange = amq.topic
mqtt.prefetch = 10
mqtt.default_user = guest
mqtt.default_pass = guest
web_mqtt.tcp.port =  20072
loopback_users = none

mqtt.tcp_listen

_options.backlog = 128
mqtt.tcp_listen_options.nodelay = true
mqtt.tcp_listen_options.linger.on      = true
mqtt.tcp_listen_options.linger.timeout = 0
mqtt.tcp_listen_options.sndbuf  = 131072
mqtt.tcp_listen_options.recbuf  = 131072

I don't know what to do to enable over 20000 concurrent connections in windows (MQTT 3.1.1).

Please give me some advice.

[michaelklishin]

See Tuning for a Large Number of Connections. Similar tuning may have to happen on the hosts that open those 20K connections.

While not directly related, RabbitMQ 3.8.2 is out of support and is 27 patch releases behind even in the 3.8 series alone.

[zhitaohB]

Thanks for your suggestions. I finally find my solution through this link https://confluence.atlassian.com/confkb/no-buffer-space-available-maximum-connections-reached-due-to-ephemeral-port-exhaustion-956142091.html

[michaelklishin]

Thank you for following up here. Client port exhaustion can be a problem, too, if you run all clients from a single machine.