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Discover how to expose your Docker's custom SFTP service publicly on port 22 in Jelastic while managing native SSH access efficiently.
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How to Change the Docker Service Port on Jelastic for Custom SFTP Access

When it comes to deploying services on cloud platforms like Jelastic, managing ports effectively is essential. One common scenario is when you want to expose a custom SFTP service on default port 22 while having another service (like SSH) running simultaneously. This guide will walk you through how to approach this issue, specifically with a focus on Jelastic's architecture.

Understanding the Problem

Imagine you've set up a custom SFTP service using a Docker container on Jelastic, but you encounter a problem:

The SFTP service is running on port 2222 inside your Docker container.

The native SSH service of the container uses port 22 for access.

Your goal is to allow public access to the SFTP service on port 22 while keeping the native SSH service secured and untouched behind the internal gateway. Unfortunately, Jelastic does not allow mapping different ports directly, which complicates things a bit.

Why You Can’t Use the Same Port for Two Services

A critical point to understand is that you cannot run two services on the same port for a single IP address. Here’s a summary of the issues:

Direct Traffic: With a public IP, any traffic hitting your node goes directly to the designated ports you've exposed. If both services tried to use port 22, you'd encounter conflicts.

Port Mapping Limitation: Jelastic allows configuration of firewall rules but doesn’t support direct port mapping from one port to another.

Possible Solutions

To achieve your goal of exposing your custom SFTP service accessible via port 22 while managing the native SSH access, here are some viable options:

1. Change the Port for Native SSH

This is the straightforward solution. You can:

Move SSH to a Different Port: Opt for a non-conflicting port for your native SSH access. For example, you could use port 2223 for SSH.

How to Implement:

Modify your Docker container configuration to run SSH on port 2223.

When accessing the container, connect directly to this new port instead of using the Jelastic SSH gateway.

2. Validate with Your Requirements

Before making the above changes, consider:

Access Stability: Ensure that using a different port for SSH doesn’t interfere with any essential management features provided by Jelastic.

Security Considerations: Examine the impact of exposing the SSH service directly to the internet. Make sure to implement firewall rules to secure it.

Conclusion

While it may seem challenging to manage service ports within the confines of a platform like Jelastic, understanding the fundamental structures helps in finding effective solutions. The key takeaways are:

You cannot run multiple services on the same port with the same public IP.

Changing the native service's port can resolve conflicts while allowing you to keep your desired configuration for your custom SFTP service.

With careful management of your Docker container’s port configurations, you can successfully expose your SFTP service without sacrificing the security and accessibility of your SSH service. Happy configuring!