Haproxy Runtime API returns empty result


I’ve configured HaProxy using the below config:

        maxconn 15000                   # Maximum concurrent connections
        nbproc 1
        pidfile /var/run/haproxy.pid
        log /dev/log local0 info
        user    root
        group   root
        tune.ssl.default-dh-param 2048
        stats socket /var/run/haproxy.stat mode 600 expose-fd listeners level user
        stats socket ipv4@*:9999 level admin  expose-fd listeners 
        log global                      #make all intefaces log by default
        option redispatch               # redispatch request originally sent to downed backend servers
        option abortonclose             # abort request if client closes output channel while waiting
        timeout server 120s

However, both below commands return empty result:

echo "help" | socat stdio /var/run/haproxy.stat
echo "help" | socat stdio tcp4-connect: 

Is there a way to fix this or cause API to return results?