# Server Pro infrastructure

### Services

The Server Pro infrastructure comprises four primary services: `sharelatex`, `git-bridge` (optional), `mongo` and `redis`. The `sharelatex` service, which runs the main Server Pro application, depends on the `mongo` and `redis` services for its database and caching/real-time functionalities and the `git-bridge` to handle the [Git integration](/on-premises/configuration/overleaf-toolkit/server-pro-only-configuration/git-integration.md) (optional). The only port published on the host machine is port 80, which is by the `sharelatex` container.

Server Pro also optionally supports [S3 compatible storage](/on-premises/configuration/overleaf-toolkit/s3.md) for project files and full project history as well as being able to proxy access to the main [Overleaf documentation site](https://www.overleaf.com/learn). For more information, see our guide on [Adding LaTeX user help](/on-premises/configuration/overleaf-toolkit/server-pro-only-configuration/adding-latex-user-help.md) pages.

{% hint style="info" %}
 If required, MongoDB and Redis can be externalised using environment variables to point to external services. For more information, see [Configuring Overleaf](/on-premises/configuration/overleaf-toolkit/environment-variables.md) if you are using Docker Compose and [Toolkit settings](/on-premises/configuration/overleaf-toolkit/toolkit-settings.md) if using the Overleaf Toolkit.
{% endhint %}

### Compiling

For [Sandboxed Compiles](/on-premises/configuration/overleaf-toolkit/server-pro-only-configuration/sandboxed-compiles.md), the `sharelatex` container will orchestrate the creation of new containers to handle project compiles, it does this via the Docker socket on the host machine. You can read more about the editor and end-to-end compile/caching process [here](/on-premises/getting-started/microservices.md#editor-and-compile-process).

### Networking

Communication between containers is facilitated through Docker's internal DNS resolution via a dedicated bridge network, and no firewalls are enabled. By default, the above services use their respective standard ports but are configurable by environment variables. The `sharelatex` container uses port 80 for external web access (served by Nginx), the `mongo` container uses port 27017 and `redis` uses port 6379.

For customers using our managed solution [Overleaf Toolkit](https://github.com/overleaf/toolkit), you can optionally [enable a TLS proxy](/on-premises/configuration/overleaf-toolkit/tls-proxy.md) for terminating HTTPS connections using Nginx via an environment variable. Alternatively, you can use your existing TLS proxy.

{% hint style="info" %}
You can view a diagram explaining the flow of requests [here](/on-premises/configuration/overleaf-toolkit/tls-proxy.md).
{% endhint %}

### Summary

* Outside the Docker network, only port 80 is accessible and bound to Nginx.\
  **Note:** The `sharelatex` container runs many [services](https://github.com/overleaf/overleaf/tree/main/services) that communicate with each other via HTTP. However, these ports are **not** accessible from outside the Docker network.
* Inside the Docker network, Overleaf services, MongoDB, Redis and Git Bridge can talk to each other freely.
* Inside [Sandboxed Compiles](/on-premises/configuration/overleaf-toolkit/server-pro-only-configuration/sandboxed-compiles.md) containers, no network is available.


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