Add basic UDP message receiving

.gitignore

@@ -0,0 +1 @@
+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "libc"
+version = "0.2.175"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a82ae493e598baaea5209805c49bbf2ea7de956d50d7da0da1164f9c6d28543"
+
+[[package]]
+name = "panic-halt"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a513e167849a384b7f9b746e517604398518590a9142f4846a32e3c2a4de7b11"
+
+[[package]]
+name = "udp-tests"
+version = "0.1.0"
+dependencies = [
+ "libc",
+ "panic-halt",
+]

Cargo.toml

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+[package]
+name = "udp-tests"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+libc = { version = "0.2.175", default-features = false }
+panic-halt = "1.0.0"
+
+[profile.dev]
+panic = "abort"
+
+[build]
+rustflags = ["-C", "link-args=-lc"]

src/main.rs

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+#![no_std]
+#![no_main]
+
+use core::{
+    alloc::{GlobalAlloc, Layout},
+    ffi::CStr,
+    ptr::null_mut,
+};
+
+extern crate alloc;
+
+use alloc::vec::Vec;
+use panic_halt as _;
+
+fn handle_error(code: i32, err: &'static core::ffi::CStr) {
+    unsafe {
+        if code == -1 {
+            libc::perror(err.as_ptr());
+            libc::exit(libc::EXIT_FAILURE);
+        }
+    }
+}
+
+struct MyAllocator;
+
+unsafe impl GlobalAlloc for MyAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        unsafe { libc::malloc(layout.size()) as *mut u8 }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        unsafe { libc::free(ptr as *mut libc::c_void) }
+    }
+}
+
+#[global_allocator]
+static GLOBAL: MyAllocator = MyAllocator;
+
+#[unsafe(no_mangle)]
+pub extern "C" fn main(_argc: isize, _argv: *const *const u8) -> isize {
+    // Since we are passing a C string the final null character is mandatory
+    unsafe {
+        libc::printf(c"Hello world!\n".as_ptr());
+
+        let socket = libc::socket(libc::AF_INET, libc::SOCK_DGRAM, libc::IPPROTO_UDP);
+
+        let address = libc::sockaddr_in {
+            sin_family: libc::AF_INET as u16,
+            sin_port: libc::htons(8080),
+            sin_addr: libc::in_addr {
+                s_addr: libc::INADDR_ANY,
+            },
+            sin_zero: [0, 0, 0, 0, 0, 0, 0, 0],
+        };
+
+        handle_error(
+            libc::bind(
+                socket,
+                &raw const address as *const libc::sockaddr,
+                core::mem::size_of::<libc::sockaddr_in>() as u32,
+            ),
+            c"bind",
+        );
+
+        let mut otus = Vec::with_capacity(10);
+
+        loop {
+            let buf = libc::malloc(16) as *mut u8;
+
+            let mut other = libc::malloc(core::mem::size_of::<libc::sockaddr_in>());
+            let mut other_size = 0;
+
+            libc::recvfrom(
+                socket,
+                buf as *mut libc::c_void,
+                1,
+                0,
+                &raw mut other as *mut libc::sockaddr,
+                &mut other_size,
+            );
+            otus.push(*buf);
+
+            libc::printf(c"Data: %s\n".as_ptr(), buf);
+
+            libc::free(buf as *mut libc::c_void);
+        }
+    }
+    0
+}