add tcp-p3 example and test (#204)

* add `tcp-p3` example and test

Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>

* keep send side open while receiving in `tcp-p3` example

Netcat likes to close the connection if the receive half is closed by the remote
host, regardless of whether stdin has been closed, and there's no obvious way to
change that behavior.  So on the client side we hold both halves open until
we've received something, which matches the p2 example behavior.

---------

Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>
Co-authored-by: Joel Dice <joel.dice@akamai.com>

Author: rvolosatovs

.gitignore

@@ -12,6 +12,7 @@ examples/http/.spin
 examples/http/http.wasm
 examples/http/proxy
 examples/http/poll_loop.py
+examples/tcp-p3/tcp.wasm
 examples/tcp/tcp.wasm
 examples/tcp/command
 examples/cli-p3/cli.wasm

examples/tcp-p3/README.md

@@ -0,0 +1,45 @@
+# Example: `tcp-p3`
+
+This is an example of how to use [componentize-py] and [Wasmtime] to build and
+run a Python-based component targetting version `0.3.0-rc-2026-01-06` of the
+[wasi-cli] `command` world and making an outbound TCP request using [wasi-sockets].
+
+[componentize-py]: https://github.com/bytecodealliance/componentize-py
+[Wasmtime]: https://github.com/bytecodealliance/wasmtime
+[wasi-cli]: https://github.com/WebAssembly/WASI/tree/v0.3.0-rc-2026-01-06/proposals/cli/wit-0.3.0-draft
+[wasi-sockets]: https://github.com/WebAssembly/WASI/tree/v0.3.0-rc-2026-01-06/proposals/sockets/wit-0.3.0-draft
+
+## Prerequisites
+
+* `Wasmtime` 41.0.3
+* `componentize-py` 0.21.0
+
+Below, we use [Rust](https://rustup.rs/)'s `cargo` to install `Wasmtime`.  If
+you don't have `cargo`, you can download and install from
+https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.3.
+
+```
+cargo install --version 41.0.3 wasmtime-cli
+pip install componentize-py==0.21.0
+```
+
+## Running the demo
+
+First, in a separate terminal, run `netcat`, telling it to listen for incoming
+TCP connections.  You can choose any port you like.
+
+```
+nc -l 127.0.0.1 3456
+```
+
+Now, build and run the example, using the same port you gave to `netcat`.
+
+```
+componentize-py -d ../../wit -w wasi:cli/command@0.3.0-rc-2026-01-06 componentize app -o tcp.wasm
+wasmtime run -Sp3 -Sinherit-network -Wcomponent-model-async tcp.wasm 127.0.0.1:3456
+```
+
+The program will open a TCP connection, send a message, and wait to receive a
+response before exiting.  You can give it a response by typing anything you like
+into the terminal where `netcat` is running and then pressing the `Enter` key on
+your keyboard.

examples/tcp-p3/app.py

@@ -0,0 +1,80 @@
+import sys
+import asyncio
+import ipaddress
+from ipaddress import IPv4Address, IPv6Address
+import wit_world
+from wit_world import exports
+from wit_world.imports.wasi_sockets_types import (
+    TcpSocket,
+    IpSocketAddress_Ipv4,
+    IpSocketAddress_Ipv6,
+    Ipv4SocketAddress,
+    Ipv6SocketAddress,
+    IpAddressFamily,
+)
+from typing import Tuple
+
+
+IPAddress = IPv4Address | IPv6Address
+
+class Run(exports.Run):
+    async def run(self) -> None:
+        args = sys.argv[1:]
+        if len(args) != 1:
+            print("usage: tcp-p3 <address>:<port>", file=sys.stderr)
+            exit(-1)
+
+        address, port = parse_address_and_port(args[0])
+        await send_and_receive(address, port)
+
+
+def parse_address_and_port(address_and_port: str) -> Tuple[IPAddress, int]:
+    ip, separator, port = address_and_port.rpartition(":")
+    assert separator
+    return (ipaddress.ip_address(ip.strip("[]")), int(port))
+
+
+def make_socket_address(address: IPAddress, port: int) -> IpSocketAddress_Ipv4 | IpSocketAddress_Ipv6:
+    if isinstance(address, IPv4Address):
+        octets = address.packed
+        return IpSocketAddress_Ipv4(Ipv4SocketAddress(
+            port=port,
+            address=(octets[0], octets[1], octets[2], octets[3]),
+        ))
+    else:
+        b = address.packed
+        return IpSocketAddress_Ipv6(Ipv6SocketAddress(
+            port=port,
+            flow_info=0,
+            address=(
+                (b[0] << 8) | b[1],
+                (b[2] << 8) | b[3],
+                (b[4] << 8) | b[5],
+                (b[6] << 8) | b[7],
+                (b[8] << 8) | b[9],
+                (b[10] << 8) | b[11],
+                (b[12] << 8) | b[13],
+                (b[14] << 8) | b[15],
+            ),
+            scope_id=0,
+        ))
+
+
+async def send_and_receive(address: IPAddress, port: int) -> None:
+    family = IpAddressFamily.IPV4 if isinstance(address, IPv4Address) else IpAddressFamily.IPV6
+
+    sock = TcpSocket.create(family)
+
+    await sock.connect(make_socket_address(address, port))
+
+    send_tx, send_rx = wit_world.byte_stream()
+    async def write() -> None:
+        await send_tx.write_all(b"hello, world!")
+
+    recv_rx, recv_fut = sock.receive()
+    async def read() -> None:
+        with recv_rx:
+            data = await recv_rx.read(1024)
+            print(f"received: {str(data)}")
+            send_tx.__exit__(None, None, None)
+    await asyncio.gather(recv_fut.read(), read(), sock.send(send_rx), write())

tests/bindings.rs

@@ -171,6 +171,25 @@ fn lint_tcp_bindings() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[test]
+fn lint_tcp_p3_bindings() -> anyhow::Result<()> {
+    let dir = tempfile::tempdir()?;
+    fs_extra::copy_items(
+        &["./examples/tcp-p3", "./wit"],
+        dir.path(),
+        &CopyOptions::new(),
+    )?;
+    let path = dir.path().join("tcp-p3");
+
+    generate_bindings(&path, "wasi:cli/command@0.3.0-rc-2026-01-06")?;
+
+    assert!(predicate::path::is_dir().eval(&path.join("wit_world")));
+
+    mypy_check(&path, ["--strict", "-m", "app"]);
+
+    Ok(())
+}
+
 fn generate_bindings(path: &Path, world: &str) -> Result<Assert, anyhow::Error> {
     Ok(cargo::cargo_bin_cmd!("componentize-py")
         .current_dir(path)

tests/componentize.rs

@@ -1,3 +1,4 @@
+use core::net::Ipv4Addr;
 use std::{
     io::Write,
     path::{Path, PathBuf},
@@ -241,21 +242,30 @@ fn sandbox_example() -> anyhow::Result<()> {
 
 #[test]
 fn tcp_example() -> anyhow::Result<()> {
+    test_tcp_example("tcp", "wasi:cli/command@0.2.0")
+}
+
+#[test]
+fn tcp_p3_example() -> anyhow::Result<()> {
+    test_tcp_example("tcp-p3", "wasi:cli/command@0.3.0-rc-2026-01-06")
+}
+
+fn test_tcp_example(name: &str, world: &str) -> anyhow::Result<()> {
     let dir = tempfile::tempdir()?;
     fs_extra::copy_items(
-        &["./examples/tcp", "./wit"],
+        &[format!("./examples/{name}").as_str(), "./wit"],
         dir.path(),
         &CopyOptions::new(),
     )?;
-    let path = dir.path().join("tcp");
+    let path = dir.path().join(name);
 
     cargo::cargo_bin_cmd!("componentize-py")
         .current_dir(&path)
         .args([
             "-d",
             "../wit",
             "-w",
-            "wasi:cli/command@0.2.0",
+            world,
             "componentize",
             "app",
             "-o",
@@ -265,16 +275,17 @@ fn tcp_example() -> anyhow::Result<()> {
         .success()
         .stdout("Component built successfully\n");
 
-    let listener = std::net::TcpListener::bind("127.0.0.1:3456")?;
+    let listener = std::net::TcpListener::bind((Ipv4Addr::LOCALHOST, 0))?;
+    let port = listener.local_addr()?.port();
 
     let tcp_handle = std::process::Command::new("wasmtime")
         .current_dir(&path)
         .args([
             "run",
-            "--wasi",
-            "inherit-network",
+            "-Sp3,inherit-network",
+            "-Wcomponent-model-async",
             "tcp.wasm",
-            "127.0.0.1:3456",
+            &format!("127.0.0.1:{port}"),
         ])
         .stdout(Stdio::piped())
         .spawn()?;