Restructure folders (#411)

other/udp-echo/Cargo.toml

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+[package]
+name = "udp-echo"
+version = "0.1.0"
+authors = ["Anton Patrushev <apatrushev@gmail.com>"]
+edition = "2018"
+
+[dependencies]
+actix = "0.10"
+actix-rt = "1.1"
+tokio = "0.2"
+tokio-util = { version = "0.3", features = [ "codec", "udp" ] }
+futures = "0.3"
+futures-util = "0.3"
+bytes = "0.5"

other/udp-echo/README.md

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+# udp-echo
+
+## Usage
+
+### server
+
+```bash
+cd examples/udp-echo
+cargo run
+# Started http server: 127.0.0.1:12345
+```
+
+### socat client
+Copy port provided in server output and run following command to communicate
+with the udp server:
+```bash
+socat - UDP4:localhost:12345
+```

other/udp-echo/src/main.rs

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+use actix::io::SinkWrite;
+use actix::{Actor, AsyncContext, Context, Message, StreamHandler};
+use bytes::Bytes;
+use bytes::BytesMut;
+use futures::stream::SplitSink;
+use futures_util::stream::StreamExt;
+use std::io::Result;
+use std::net::SocketAddr;
+use tokio::net::UdpSocket;
+use tokio_util::codec::BytesCodec;
+use tokio_util::udp::UdpFramed;
+
+type SinkItem = (Bytes, SocketAddr);
+type UdpSink = SplitSink<UdpFramed<BytesCodec>, SinkItem>;
+
+struct UdpActor {
+    sink: SinkWrite<SinkItem, UdpSink>,
+}
+impl Actor for UdpActor {
+    type Context = Context<Self>;
+}
+
+#[derive(Message)]
+#[rtype(result = "()")]
+struct UdpPacket(BytesMut, SocketAddr);
+
+impl StreamHandler<UdpPacket> for UdpActor {
+    fn handle(&mut self, msg: UdpPacket, _: &mut Context<Self>) {
+        println!("Received: ({:?}, {:?})", msg.0, msg.1);
+        self.sink.write((msg.0.into(), msg.1)).unwrap();
+    }
+}
+
+impl actix::io::WriteHandler<std::io::Error> for UdpActor {}
+
+#[actix_rt::main]
+async fn main() {
+    let addr: SocketAddr = "127.0.0.1:0".parse().unwrap();
+    let sock = UdpSocket::bind(&addr).await.unwrap();
+    println!(
+        "Started udp server on: 127.0.0.1:{:?}",
+        sock.local_addr().unwrap().port()
+    );
+    let (sink, stream) = UdpFramed::new(sock, BytesCodec::new()).split();
+    UdpActor::create(|ctx| {
+        ctx.add_stream(stream.filter_map(
+            |item: Result<(BytesMut, SocketAddr)>| async {
+                item.map(|(data, sender)| UdpPacket(data, sender)).ok()
+            },
+        ));
+        UdpActor {
+            sink: SinkWrite::new(sink, ctx),
+        }
+    });
+
+    actix_rt::Arbiter::local_join().await;
+}