Added an example for `webtransport-go` #220

kavin81 · 2025-12-30T06:31:12Z

this PR is for add an example #154
it's a simple hello-world example where if client sends "hello" -> server responds with "World!"
also just fixed a misc typo in comments

macroscopeapp · 2025-12-30T06:32:06Z

Add a runnable helloWorld example with a WebTransport server on `:4430` at path `/webtransport`, a CLI client using new `common` helpers, and a 1024-byte per-stream read limit

Introduce an examples module with a server and client demonstrating bidirectional streams, including self-signed TLS setup and an insecure client TLS config; update documentation and adjust the webtransport.Server ApplicationProtocols comment.

📍Where to Start

Start with the server entry point in main.go, then follow session handling in handleSession and per-stream logic in handleStream.

Macroscope summarized e5f4442.

Copilot

Pull request overview

This PR adds a hello world example for the webtransport-go library and fixes a documentation URL in server.go. The example demonstrates basic bidirectional communication where a client can send messages to a server via WebTransport streams, with the server responding "world!" to "hello" messages.

Adds a complete hello world example with client, server, and shared configuration code
Includes comprehensive documentation with usage instructions and mermaid flowcharts
Updates the server.go comment to use a more specific URL format

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
server.go	Updates documentation URL to use a more specific anchor link format
examples/go.mod	Defines the Go module for examples with dependencies
examples/go.sum	Contains checksums for example dependencies
examples/README.md	Provides overview of available examples
examples/helloWorld/README.md	Comprehensive documentation for the hello world example
examples/helloWorld/common/config.go	Shared configuration including TLS setup and server settings
examples/helloWorld/server/main.go	WebTransport server implementation
examples/helloWorld/client/main.go	Interactive WebTransport client implementation

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Copilot · 2025-12-30T06:34:09Z

examples/helloWorld/README.md

+Server response: world!
+
+Enter message: test
+Server response: echo: test


The example output on line 42 shows "Server response: echo: test", but the actual server implementation (server/main.go line 75) sends "I only respond to 'hello' with 'world!'" for any non-"hello" message. The example output should match the actual server behavior.

Copilot · 2025-12-30T06:34:10Z

examples/helloWorld/common/config.go

+		SerialNumber: big.NewInt(1),
+		NotBefore:    time.Now(),
+		NotAfter:     time.Now().Add(365 * 24 * time.Hour),
+		DNSNames:     []string{"localhost"},


The self-signed certificate lacks required basic fields for x509.Certificate. The certificate should include KeyUsage and ExtKeyUsage fields to properly identify its purpose. Additionally, consider adding IsCA: false to explicitly indicate this is not a CA certificate.

Suggested change

SerialNumber: big.NewInt(1),

NotBefore: time.Now(),

NotAfter: time.Now().Add(365 * 24 * time.Hour),

DNSNames: []string{"localhost"},

SerialNumber: big.NewInt(1),

NotBefore: time.Now(),

NotAfter: time.Now().Add(365 * 24 * time.Hour),

DNSNames: []string{"localhost"},

KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,

ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},

IsCA: false,

BasicConstraintsValid: true,

Copilot · 2025-12-30T06:34:10Z

examples/helloWorld/server/main.go

+func handleStream(stream *webtransport.Stream) {
+	defer stream.Close()
+
+	data, err := io.ReadAll(stream)


Using io.ReadAll on an incoming stream without any size limit or timeout can lead to resource exhaustion if a malicious client sends a very large message. Consider implementing a maximum message size limit or using io.LimitReader to protect against DoS attacks.

Copilot · 2025-12-30T06:34:10Z

examples/helloWorld/server/main.go

@@ -0,0 +1,86 @@
+package server


The package declaration should be "main" instead of "server" for an executable program. Go programs that should be run with "go run" must be in package main with a main() function.

Suggested change

package server

package main

Copilot · 2025-12-30T06:34:11Z

examples/helloWorld/client/main.go

@@ -0,0 +1,96 @@
+package client


The package declaration should be "main" instead of "client" for an executable program. Go programs that should be run with "go run" must be in package main with a main() function.

Suggested change

package client

package main

Copilot · 2025-12-30T06:34:11Z

examples/helloWorld/README.md

+    B --> C[Connected!]
+    C --> D[Get User Input]
+    D --> E{quit?}
+    E -->|Yes| F[lose & Exit]


There is a typo in the flowchart. "lose" should be "Close" to properly indicate "Close & Exit".

Suggested change

E -->|Yes| F[lose & Exit]

E -->|Yes| F[Close & Exit]

Copilot · 2025-12-30T06:34:11Z

examples/helloWorld/README.md

+
+1. **Server** listens for WebTransport connections
+2. **Client** connects and opens streams for each message
+3. Server responds with "world!" for "hello", otherwise echoes the message


The README description on line 21 states the server "echoes the message" for non-"hello" messages, but the actual implementation in server/main.go (line 75) sends "I only respond to 'hello' with 'world!'" instead of echoing. The documentation should match the actual behavior.

Copilot · 2025-12-30T06:34:12Z

examples/helloWorld/README.md

+
+```mermaid
+flowchart TD
+    A[Start Server] --> B[Listen on :4433]


The port number in the flowchart shows ":4433", but the actual server configuration in common/config.go uses port "4430" (line 15). The documentation should reflect the correct port number.

Suggested change

A[Start Server] --> B[Listen on :4433]

A[Start Server] --> B[Listen on :4430]

Copilot · 2025-12-30T06:34:12Z

examples/helloWorld/README.md

+    E --> F[Read Message]
+    F --> G{hello?}
+    G -->|Yes| H[Send: world!]
+    G -->|No| I[Send: echo message]


The flowchart description on line 59 shows "Send: echo message" which does not match the actual server implementation. The server sends "I only respond to 'hello' with 'world!'" for non-"hello" messages, not an echo of the message.

kavin81 · 2026-01-02T19:16:34Z

@marten-seemann hi I'm sorry if your busy (rightfully so); TLDR in case you didnt see the PR / missed it - do you have any feedback on it?

kavin81 added 2 commits December 29, 2025 18:37

docs: fix ALPN URL in code comments

09af539

feat: add Hello World example with WebTransport client and server

f6e242d

Copilot AI review requested due to automatic review settings December 30, 2025 06:31

Copilot started reviewing on behalf of kavin81 December 30, 2025 06:31 View session

Copilot AI reviewed Dec 30, 2025

View reviewed changes

fix: minor issues & typos

e5f4442

	A[Start Server] --> B[Listen on :4433]
	A[Start Server] --> B[Listen on :4430]

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Added an example for webtransport-go #220

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kavin81 commented Dec 30, 2025

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Add a runnable helloWorld example with a WebTransport server on :4430 at path /webtransport, a CLI client using new common helpers, and a 1024-byte per-stream read limit

📍Where to Start

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Added an example for `webtransport-go` #220

Added an example for `webtransport-go` #220

macroscopeapp bot commented Dec 30, 2025 •

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Add a runnable helloWorld example with a WebTransport server on `:4430` at path `/webtransport`, a CLI client using new `common` helpers, and a 1024-byte per-stream read limit

kavin81 commented Jan 2, 2026 •

edited

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