TEK Steam Client

Disclaimer: This project is not affiliated with Valve Corporation and their official Steam client

tek-steamclient is an open-source C library that implements some parts of a Steam client, most notably the application manager, that allows downloading, verifying and updating Steam applications. It is written in C and C++ and can be built for Windows, Linux (including Android via e.g. Termux) and MacOS.

This repository also provides tek-sc-cli, simple command-line interface on top of tek-steamclient, somewhat similar to steamcmd in functionality.

Features

• Cross-platform, has been tested on x86_64 and AArch64 CPU architectures, might be able to be compiled for others
• Does not require Steam application to be installed, and in fact offers alternative to some of its functionality
• Can utilize tek-s3 servers to work with applications owned by other people, without logging into their accounts locally
• Efficiently utilizes modern OS features to achieve best I/O performance
• Uses homemade update algorithms that allow utilizing much less disk space for patching than official Steam client does

Installing

Windows

There are statically linked binaries for libtek-steamclient-X.dll and tek-sc-cli.exe in releases, in archive named tek-steamclient-X.Y.Z-win-x86_64.zip. They do not have any external dependencies other than Windows system DLLs, and are recommended for regular use. These binaries are built in MSYS2 TEK-X86_64 environment and signed by Nuclearist's code signing certificate, which in turn is signed by TEK CA, so they will be trusted by OS if TEK CA certificate is.

Linux

There is tek-sc-cli-x86_64.AppImage in releases, which is built in a Debian Stable container and signed by Nuclearist's GPG key. It can be run with TEK_SC_USE_SYSTEM_LIBS=1 environment variable to prefer system libraries over bundled ones.

To use the library, you have to install a package for your distro listed below, or build from source if it's not there.

Distro	Package
Gentoo	games-util/tek-steamclient from tek-overlay

Using

tek-steamclient consists of several APIs:

• Application manager (app_manager, am) - Higher level API, uses all the other ones under the hood. Manages Steam item installations in a directory, provides functions for installing, updating, verifying, uninstalling them. Recommended to use unless there is a good reason not to.
• SteamPipe API (steampipe, sp) - Focused on downloading and decoding data from SteamPipe content servers (manifests, patches, chunks).
• Content API (content, [dm, dp, vc, dd]) - provides structures and functions for parsing/creating, serializing and deserializing Steam content files in tek-steamclient's own formats: depot manifests, depot patches, verification caches, and depot deltas.
• tek-s3 client API (s3_client, s3c) - provides integration with tek-s3 servers, allowing to fetch manifest request codes, depot decryption keys and PICS access tokens from them. Application manager uses it with servers synchronized via tek_sc_s3c_sync_manifest
• CM client API (cm) - provides client for Steam CM servers that manage account-related functionality. Application manager implicitly uses it with an anonymous account to fetch some of the data it needs.

For end users, tek-sc-cli program provides thin command-line interface for application manager and tek-s3 client APIs. Use its --help argument or help command to list available commands.

For developers, libtek-steamclient interfaces are provided via header files:

• base.h - Basic declarations used by all APIs and library context functions.
• error.h - Declarations of types and functions for error handling, used by all APIs.
• os.h - OS-specific type declarations used by some of the APIs.
• cm.h - CM client API.
• s3c.h - tek-s3 client API.
• content.h - Content API.
• sp.h - SteamPipe API.
• am.h - Application manager API.

Project structure

• include - C header files providing public library interface.
• pkgfiles - Files or file templates for package managers to use.
• po - Localization files.
• protos - Protobuf definition files for various Steam messages. Based on data from SteamDatabase/Protobufs project.
• res - Resource files for Windows binaries
• src - Source code:
  • cli - tek-sc-cli program source code
  • common - headers used by both libtek-steamclient and tek-sc-cli
  • lib - libtek-steamclient library source code
• subprojects - Meson subproject directory. The repository includes wrap files and package files for dependencies that do not have their own packages in major distros. Currently the only such is ValveFileVDF