ADd client and README

problem_04/README.md

@@ -0,0 +1,32 @@
+## Usage
+
+### Star the server
+```bash
+$ cargo run --bin server
+```
+
+or with logs:
+
+```bash
+$ RUST_LOG=info cargo run --bin server
+```
+
+### Test with the client
+
+```bash
+$ cargo run --bin client 127.0.0.1:1222 "foo=bar"
+```
+
+## Example output
+
+```bash
+$ cargo run --bin client 127.0.0.1:1222 "foo=bar"
+    Finished dev [unoptimized + debuginfo] target(s) in 0.02s
+     Running `target/debug/client '127.0.0.1:1222' foo=bar`
+Insert request sent. No response expected.
+
+$ cargo run --bin client 127.0.0.1:1222 "foo"
+    Finished dev [unoptimized + debuginfo] target(s) in 0.02s
+     Running `target/debug/client '127.0.0.1:1222' foo`
+Received response: foo=bar
+```

problem_04/bin/client.rs

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+use std::env;
+use std::error::Error;
+use std::net::SocketAddr;
+use std::time::Duration;
+use tokio::net::UdpSocket;
+
+const MAX_DATAGRAM_SIZE: usize = 1000;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() < 3 {
+        println!("Usage: {} <server-ip:port> <request>", args[0]);
+        return Ok(());
+    }
+
+    let server_addr: SocketAddr = args[1].parse()?;
+    let request = args[2].clone();
+
+    let local_addr = if server_addr.is_ipv4() {
+        "0.0.0.0:0"
+    } else {
+        "[::]:0"
+    };
+
+    let socket = UdpSocket::bind(local_addr).await?;
+    socket.connect(server_addr).await?;
+
+    socket.send(request.as_bytes()).await?;
+
+    if request.contains('=') {
+        println!("Insert request sent. No response expected.");
+    } else {
+        let mut buf = vec![0; MAX_DATAGRAM_SIZE];
+        let _ = tokio::time::timeout(Duration::from_secs(1), socket.recv(&mut buf)).await?;
+
+        let response = String::from_utf8_lossy(&buf);
+        println!("Received response: {}", response);
+    }
+
+    Ok(())
+}

problem_04/src/lib.rs

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-fn main() {
-    println!("Hello, world!");
-}