EC2 port 80 refused to connect on public IP but can connect using private IP

Nandu Kkd

6/15/24, 9:44 AM

Question simplified

I can do curl {publicip}:4321 but not curl {publicip}:80 or curl {publicip}. But from the server's ssh, i can run curl {privateip}:80 and curl localhost:80 without any issues. And also, both port 80 and port 4321 are added to inbound rules in security group. Why is that happening?

The Story

I'm new to AWS EC2. I recently created an EC2 t4g nano instance, and ran a NodeJS server using PM2. The server listens on port 4321. Then using iptables, I redirected port 80 to port 4321. Then in security groups, I added inbound rule from "Anywhere IP" to port 80 (HTTP).

Everything was working, I was able to connect using the instance's public IP to the server until today morning, when I suddenly wasn't able to even SSH to the server. The instance status in AWS console showed as 'running', but in status check, 1/2 was not successfull. It showed "Instance reachability failed". Then, I tried to restart the instance, it worked and then I could SSH it.

Now, I restarted PM2, and then again added the redirecting rule to iptables. But now, I cant connect to port 80 using public IP.

I can run curl localhost:80 and curl {privateip}:80, it connects without any issues. When I run curl {publicip}:80 or curl {publicip} it shows 'Connection refused`. As I said, port 80 already exists in the security group's inbound rules.

I added port 4321 to the inbound rules of the security group, and I can connect without any issues using curl {publicip}:4321 but not curl ${publicip}:80. How's that possible? Did I miss something?

0 + 0

iptables

connection-refused

security-groups

aws-ec2

Elon Musk

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EN: EC2 port 80 refused to connect on public IP but can connect using private IP

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