Networking 101 For Aspiring Game Developers

Getting Started with Networking for Games

Developing networked games requires an understanding of network architecture, choosing the right network model like client-server or peer-to-peer, selecting a networking library, and leveraging common networking technologies used in games.

Understanding Network Architecture

The network architecture for games refers to the overall design of hardware devices, networking protocols, topologies, and infrastructure required to enable communication between game clients and servers over the internet. Key components include:

• Networking hardware – routers, switches, servers, which route and transmit data.
• Networking protocols – rules for communication over networks, like TCP/IP, UDP, and ICMP.
• Topologies – the layout of the network such as peer-to-peer, client-server, or hybrid models.
• Infrastructure – the physical cabling, wireless networks, data centers, and ISPs that provide connectivity.

Understanding these core building blocks is essential for engineering robust networked games.

Choosing Between Client-Server and P2P

The two most common network topologies used in games are client-server and peer-to-peer models:

• Client-Server – clients connect to a central server. Servers are authoritative over game state updates and synchronization. Scales better than P2P. Used in MMOs, multiplayer shooters etc.
• P2P (Peer-to-Peer) – clients connect directly without a central server. Each peer maintains the game state based on updates from other peers. Lower infrastructure costs but doesn’t scale as well. Used in small multiplayer games.

Factors like number of players, gameplay requirements, cost, scalability etc. determine the right choice of topology.

Selecting a Networking Library

Instead of coding network functionality from scratch, developers can leverage existing third-party networking libraries and APIs like:

• Photon – offers a free tier and integrates well across mobile, console and PC platforms with APIs in C++, Unity, C# etc.
• UNet – Unity’s built-in high level networking API with client-server and P2P support.
• GameLift – AWS managed service for deploying servers, peer matching, scaling capabilities etc.

The choice depends on the game engine/platform, architecture, features, pricing and learning curve.

Common Networking Technologies Used in Games

Some popular technologies for networked games include:

• TCP – Transmission Control Protocol provides reliable, ordered data delivery using acknowledgements and timeouts.
• UDP – User Datagram Protocol offers faster unmatched transmission without guarantees for ordering or reliability.
• Websockets – Persistent connections over TCP with lower overhead vs HTTP polling using full-duplex communication.
• WebRTC – Enables direct P2P connectivity between browsers for applications like multiplayer games with audio/video chat.

Developers choose the right protocols based on reliability needs and gameplay constraints.

Key Networking Concepts

Some foundational networking concepts game developers need to master include:

Latency and Bandwidth

Latency is the delay between sending packets from source to destination while bandwidth determines maximum throughput. High latency and low bandwidth degrades multiplayer gaming performance. Methods to address this include latency masking, compensation techniques, and bandwidth optimization.

Packet Loss

Packet loss is when data packets fail to reach their destination. TCP handles this using acknowledgements, timeouts and retransmissions whereas UDP does not guarantee packet delivery so games need custom logic. Packet loss compensation includes dead reckoning, client-side prediction, lag compensation etc.

Network Topologies

Network topology optimization is vital for lowering latency in multiplayer games. Some common topologies include:

• Ring – Connects nodes in a circular loop where each node communicates with adjacent nodes only.
• Star – Has a central node that connects other points. Used extensively in client-server model for games.
• Mesh – Nodes connect directly to as many other nodes as possible. Provides high redundancy but difficult to scale.

NAT Punchthrough

NAT Punchthrough techniques enable direct P2P connectivity between clients behind Network Address Translation (NAT) firewalls and routers. This avoids routing traffic via intermediate internet servers for better gaming performance.

Serialization and Marshaling

Serialization converts game data structures into format suitable for transmission over the network like JSON or protobuffers while marshaling decompresses data back into objects on the receiving end. Optimal data serialization mechanisms minimize bandwidth usage in games.

Implementing Basic Multiplayer Functionality

Key aspects for adding basic multiplayer support in games include:

Establishing Connections

Setting up network connectivity between game clients and servers is the first step. This involves protocols like TCP/IP, resolving IP addresses via DNS, opening sockets for endpoints, and negotiating connections.

Sending and Receiving Data

Once connections are established, game data can be transmitted using packets. The format and frequency of these update packets impact overall performance. UDP is widely used although TCP offers more reliability.

Synchronizing Game State

Keeping the game state in sync across different players is crucial for multiplayer gaming. This requires efficient state propagation, latency compensation techniques, optimistic updates, interpolation and client-side prediction.

Handling Disconnections

Robust reconnection and retry logic is vital when players get disconnected due to network issues, along with keeping states consistent post-reconnection. Saving player progress, game checkpoints also improves tolerance for disconnections.

Advanced Topics

Some advanced concepts for improving gameplay quality involve:

Encryption and Security

Encryption using TLS/SSL helps secure sensitive game data during transit protecting aspects like player authentication, virtual economy from cheating. AWS, Google Cloud offer managed encrypted connections.

Lobby Systems

Game lobbies allow grouping players before the start of a multiplayer game for social engagement. This requires discovery protocols, peer matching algorithms, chat functionality etc.

Matchmaking Algorithms

Skill-based matchmaking maximizes player enjoyment by forming competitive pairings or teams. This uses statistical inference models leveraging data on metrics like player levels, win rates, experience etc.

Authoritative vs Distributed Servers

Authoritative servers validate all game updates sent by clients to ensure cheating prevention whereas distributed servers provide more scalability, redundancy but have higher synchronization complexity due to lack of centralized authority.

Scaling and Load Balancing

Scaling multiplayer servers across multiple nodes provides cost efficiency and supports more concurrent players. Load balancing helps distribute network traffic across servers optimally using algorithms like round-robin, least connections etc.

Handling Cheating and Hacks

Cheating detection involves monitoring anomalous gameplay metrics, randomness checks, hardware bans etc. Anti-cheating encryption, obfuscation mechanisms prevent hacking game client binaries or memory. Server authoritativeness also limits cheating.

Further Learning

Games programmers looking to enhance their network programming skills can refer to:

Useful Books and Online Courses

Books like “Multiplayer Game Programming”, Game Networking courses on Coursera, Udemy etc. offer deeper dives into concepts.

Open Source Projects to Study

GitHub has many community developed games showcasing various networking mechanics which serve as practical guides.

Finding a Network Programming Mentor

Learning directly from an experienced networking programmer accelerates understanding of nuances vs self-study.

Attending Developer Conferences

GDC, Devcom are conferences offering dedicated networking sessions/workshops to learn from industry experts.