What is Port 443?

Port 443 is the default port used for HTTPS (Hypertext Transfer Protocol Secure) traffic. It operates on the TCP (Transmission Control Protocol) and serves as the secure gateway for web communication over the Internet. Whenever a browser initiates an HTTPS request, it targets the server via TCP Port 443.

Role of TLS/SSL in Port 443
Behind the scenes, Port 443 relies on SSL/TLS protocols to encrypt the connection between the client (browser) and the server. When a browser connects to a server over HTTPS, a TLS handshake occurs on Port 443. During this handshake:

The server presents its digital certificate (usually X.509).

The client verifies the certificate's authenticity and extracts the public key.

Both parties agree on cipher suites and establish a session key.
This session key then encrypts all subsequent communication over Port 443.

This process prevents man-in-the-middle attacks, packet sniffing, and data tampering by ensuring confidentiality, authenticity, and integrity.

Firewall and Networking Context
In most firewalls, Port 443 must be explicitly allowed for inbound and outbound HTTPS traffic. Network administrators typically configure routers, switches, and firewalls to forward HTTPS requests on this port to web servers inside a secure DMZ (demilitarized zone).

Moreover, many load balancers and reverse proxies (like NGINX, HAProxy) handle SSL termination on Port 443 before passing decrypted traffic to internal services.

Conclusion
Port 443 is not just another TCP port; it's the foundation of secure web communication. Without it, HTTPS wouldn't exist, and the modern web wouldn't be trusted.

Let me know if you'd like to expand this into a developer-focused guide or include diagrams!

You can read more about it here - https://cheapsslweb.com/blog/port-443-https/