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//! An example of hooking up stdin/stdout to either a TCP or UDP stream.
//!
//! This example will connect to a socket address specified in the argument list
//! and then forward all data read on stdin to the server, printing out all data
//! received on stdout. An optional `--udp` argument can be passed to specify
//! that the connection should be made over UDP instead of TCP, translating each
//! line entered on stdin to a UDP packet to be sent to the remote address.
//!
//! Note that this is not currently optimized for performance, especially
//! around buffer management. Rather it's intended to show an example of
//! working with a client.
//!
//! This example can be quite useful when interacting with the other examples in
//! this repository! Many of them recommend running this as a simple "hook up
//! stdin/stdout to a server" to get up and running.
#![deny(warnings)]
extern crate tokio;
extern crate tokio_io;
extern crate futures;
extern crate bytes;
use std::env;
use std::io::{self, Read, Write};
use std::net::SocketAddr;
use std::thread;
use tokio::prelude::*;
use futures::sync::mpsc;
fn main() {
// Determine if we're going to run in TCP or UDP mode
let mut args = env::args().skip(1).collect::<Vec<_>>();
let tcp = match args.iter().position(|a| a == "--udp") {
Some(i) => {
args.remove(i);
false
}
None => true,
};
// Parse what address we're going to connect to
let addr = args.first().unwrap_or_else(|| {
panic!("this program requires at least one argument")
});
let addr = addr.parse::<SocketAddr>().unwrap();
// Right now Tokio doesn't support a handle to stdin running on the event
// loop, so we farm out that work to a separate thread. This thread will
// read data (with blocking I/O) from stdin and then send it to the event
// loop over a standard futures channel.
let (stdin_tx, stdin_rx) = mpsc::channel(0);
thread::spawn(|| read_stdin(stdin_tx));
let stdin_rx = stdin_rx.map_err(|_| panic!()); // errors not possible on rx
// Now that we've got our stdin read we either set up our TCP connection or
// our UDP connection to get a stream of bytes we're going to emit to
// stdout.
let stdout = if tcp {
tcp::connect(&addr, Box::new(stdin_rx))
} else {
udp::connect(&addr, Box::new(stdin_rx))
};
// And now with our stream of bytes to write to stdout, we execute that in
// the event loop! Note that this is doing blocking I/O to emit data to
// stdout, and in general it's a no-no to do that sort of work on the event
// loop. In this case, though, we know it's ok as the event loop isn't
// otherwise running anything useful.
let mut out = io::stdout();
tokio::run({
stdout
.for_each(move |chunk| {
out.write_all(&chunk)
})
.map_err(|e| println!("error reading stdout; error = {:?}", e))
});
}
mod codec {
use std::io;
use bytes::{BufMut, BytesMut};
use tokio::codec::{Encoder, Decoder};
/// A simple `Codec` implementation that just ships bytes around.
///
/// This type is used for "framing" a TCP/UDP stream of bytes but it's really
/// just a convenient method for us to work with streams/sinks for now.
/// This'll just take any data read and interpret it as a "frame" and
/// conversely just shove data into the output location without looking at
/// it.
pub struct Bytes;
impl Decoder for Bytes {
type Item = BytesMut;
type Error = io::Error;
fn decode(&mut self, buf: &mut BytesMut) -> io::Result<Option<BytesMut>> {
if buf.len() > 0 {
let len = buf.len();
Ok(Some(buf.split_to(len)))
} else {
Ok(None)
}
}
}
impl Encoder for Bytes {
type Item = Vec<u8>;
type Error = io::Error;
fn encode(&mut self, data: Vec<u8>, buf: &mut BytesMut) -> io::Result<()> {
buf.put(&data[..]);
Ok(())
}
}
}
mod tcp {
use tokio;
use tokio::net::TcpStream;
use tokio::prelude::*;
use tokio::codec::Decoder;
use bytes::BytesMut;
use codec::Bytes;
use std::io;
use std::net::SocketAddr;
pub fn connect(addr: &SocketAddr,
stdin: Box<Stream<Item = Vec<u8>, Error = io::Error> + Send>)
-> Box<Stream<Item = BytesMut, Error = io::Error> + Send>
{
let tcp = TcpStream::connect(addr);
// After the TCP connection has been established, we set up our client
// to start forwarding data.
//
// First we use the `Io::framed` method with a simple implementation of
// a `Codec` (listed below) that just ships bytes around. We then split
// that in two to work with the stream and sink separately.
//
// Half of the work we're going to do is to take all data we receive on
// `stdin` and send that along the TCP stream (`sink`). The second half
// is to take all the data we receive (`stream`) and then write that to
// stdout. We'll be passing this handle back out from this method.
//
// You'll also note that we *spawn* the work to read stdin and write it
// to the TCP stream. This is done to ensure that happens concurrently
// with us reading data from the stream.
Box::new(tcp.map(move |stream| {
let (sink, stream) = Bytes.framed(stream).split();
tokio::spawn(stdin.forward(sink).then(|result| {
if let Err(e) = result {
panic!("failed to write to socket: {}", e)
}
Ok(())
}));
stream
}).flatten_stream())
}
}
mod udp {
use std::io;
use std::net::SocketAddr;
use tokio;
use tokio::net::{UdpSocket, UdpFramed};
use tokio::prelude::*;
use bytes::BytesMut;
use codec::Bytes;
pub fn connect(&addr: &SocketAddr,
stdin: Box<Stream<Item = Vec<u8>, Error = io::Error> + Send>)
-> Box<Stream<Item = BytesMut, Error = io::Error> + Send>
{
// We'll bind our UDP socket to a local IP/port, but for now we
// basically let the OS pick both of those.
let addr_to_bind = if addr.ip().is_ipv4() {
"0.0.0.0:0".parse().unwrap()
} else {
"[::]:0".parse().unwrap()
};
let udp = UdpSocket::bind(&addr_to_bind)
.expect("failed to bind socket");
// Like above with TCP we use an instance of `Bytes` codec to transform
// this UDP socket into a framed sink/stream which operates over
// discrete values. In this case we're working with *pairs* of socket
// addresses and byte buffers.
let (sink, stream) = UdpFramed::new(udp, Bytes).split();
// All bytes from `stdin` will go to the `addr` specified in our
// argument list. Like with TCP this is spawned concurrently
let forward_stdin = stdin.map(move |chunk| {
(chunk, addr)
}).forward(sink).then(|result| {
if let Err(e) = result {
panic!("failed to write to socket: {}", e)
}
Ok(())
});
// With UDP we could receive data from any source, so filter out
// anything coming from a different address
let receive = stream.filter_map(move |(chunk, src)| {
if src == addr {
Some(chunk.into())
} else {
None
}
});
Box::new(future::lazy(|| {
tokio::spawn(forward_stdin);
future::ok(receive)
}).flatten_stream())
}
}
// Our helper method which will read data from stdin and send it along the
// sender provided.
fn read_stdin(mut tx: mpsc::Sender<Vec<u8>>) {
let mut stdin = io::stdin();
loop {
let mut buf = vec![0; 1024];
let n = match stdin.read(&mut buf) {
Err(_) |
Ok(0) => break,
Ok(n) => n,
};
buf.truncate(n);
tx = match tx.send(buf).wait() {
Ok(tx) => tx,
Err(_) => break,
};
}
}