Network Programming on Raspberry Pi

Send a reading from your Pi to another program, then to a browser. Explore how the protocols fit together before building small C++ programs.

How TCP, UDP, HTTP and TLS fit together

Choose a protocol. Follow its path from your application to the network.

HTTPS with HTTP/1.1 or HTTP/2: HTTP → TLS → TCP → IP.

HTTPS with HTTP/3: HTTP/3 → QUIC → UDP → IP. QUIC integrates the TLS 1.3 handshake.

WebSocket provides two-way messages; WSS adds protection. DTLS protects datagram communication.

UDP and TCP: what reaches your program?

Send 1 → 2 → 3. Try delaying or losing 2, and compare the arrival order with the data available to the application.

If 2 is delayed, UDP can deliver 1 → 3 → 2. TCP holds later bytes until the missing bytes arrive, making them available in order: 1 → 2 → 3.

If 2 is lost, UDP does not resend it. TCP attempts recovery by retransmission.

UDP preserves message boundaries. TCP provides an ordered byte stream; your code still needs to find message boundaries.

About these diagrams

Numbers identify UDP messages or consecutive TCP byte ranges, not TCP application messages. The example shows successful TCP recovery; real connections can time out or fail. Steps illustrate events, not their timing.

The stack explorer shows selected protocol mappings. Its WebSocket paths use an HTTP/1.1 opening handshake. QUIC integrates TLS for its handshake and protects its own packets.

Specifications: UDP, TCP, HTTP, WebSocket, DTLS, QUIC, TLS in QUIC, HTTP/3.

What you will build

Part 1: Foundations

• Tools and Your First Program
• Addresses, Ports and Sockets

Part 2: UDP

• Your First UDP Exchange
• Datagram Boundaries and Buffer Sizes
• Loss, Duplicates and Reordering

Part 3: TCP

• Your First TCP Connection
• Message Boundaries in a TCP Stream
• Disconnection and Timeouts
• Multiple TCP Connections

Part 4: HTTP

• Your First HTTP Request
• HTTP Headers and Body Length
• A Small HTTP Server
• Chunked HTTP Bodies
• HTTP Connection Reuse

Part 5: TLS and HTTPS

• Your First Verified TLS Connection
• Certificates, Hostnames and Trust
• Your First HTTPS Request

Part 6: WebSocket

• Opening Handshake
• Text Frames and Clean Closure
• Ping and Pong
• Extended Payload Lengths
• Fragmented Messages
• WebSocket over Verified TLS

Part 7: DTLS

• Your First Verified DTLS Exchange
• Message IDs and Explicit Retries

Part 8: QUIC and HTTP/3

• QUIC Streams and Toolchain
• Your First Verified QUIC Stream
• Multiple QUIC Streams
• Your First HTTP/3 Request

C++ examples on GitHub use CMake and run on one Pi. Basic C++ is enough; no additional hardware is needed.

Check yourself: If 3 arrives before 2, which protocol waits before making those later bytes available to your program?

Answer

TCP. UDP can deliver message 3 before message 2.

Start with Tools and Your First Network Program.