Unable connect via port knocking

Question

I am trying to set up port knocking on my server to enhance security. I've configured my firewall rules to use port knocking, where I have to connect to specific ports in a specific sequence before being allowed to connect to SSH.

Here are the relevant portions of my firewall rules:

Chain INPUT (policy DROP)
target     prot opt source               destination
DROP       tcp  --  anywhere             anywhere             tcp dpt:1001 recent: SET name: RECENT side: source mask: 255.255.255.255
DROP       tcp  --  anywhere             anywhere             tcp dpt:2002 recent: CHECK seconds: 60 name: RECENT side: source mask: 255.255.255.255
SSH        tcp  --  anywhere             anywhere             tcp dpt:ssh recent: CHECK seconds: 60 name: RECENT side: source mask: 255.255.255.255
ACCEPT     all  --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere

Chain SSH (1 references)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh

However, I am unable to connect to my server even after successfully performing the port knocking sequence.

I've tried the following steps:

1. Sent TCP packets to port 1001 followed by port 2002.
2. Waited for a few moments.
3. Attempted to connect to SSH port (usually 22).

# Port Knocking
nc -zv server_ip 1001

# Wait a few seconds
nc -zv server_ip 2002

# SSH Connection
ssh user@server_ip

Despite these steps, I'm unable to establish an SSH connection.

What could be causing this issue? Are there any additional configurations or troubleshooting steps I should consider?

Thank you for your assistance!