root@rss:/home/admin# ss -tulpn | grep 6556
tcp LISTEN 0 4096 *:6556 *:* users:(("systemd",pid=1,fd=60))
root@rss:/home/admin# systemctl --version
systemd 245 (245.4-4ubuntu3.17)
+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid