1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
|
//! A "hello world" echo server with Tokio
//!
//! This server will create a TCP listener, accept connections in a loop, and
//! write back everything that's read off of each TCP connection.
//!
//! Because the Tokio runtime uses a thread pool, each TCP connection is
//! processed concurrently with all other TCP connections across multiple
//! threads.
//!
//! To see this server in action, you can run this in one terminal:
//!
//! cargo run --example echo
//!
//! and in another terminal you can run:
//!
//! cargo run --example connect 127.0.0.1:8080
//!
//! Each line you type in to the `connect` terminal should be echo'd back to
//! you! If you open up multiple terminals running the `connect` example you
//! should be able to see them all make progress simultaneously.
#![deny(warnings)]
extern crate tokio;
use tokio::io;
use tokio::net::TcpListener;
use tokio::prelude::*;
use std::env;
use std::net::SocketAddr;
fn main() -> Result<(), Box<std::error::Error>> {
// Allow passing an address to listen on as the first argument of this
// program, but otherwise we'll just set up our TCP listener on
// 127.0.0.1:8080 for connections.
let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
let addr = addr.parse::<SocketAddr>()?;
// Next up we create a TCP listener which will listen for incoming
// connections. This TCP listener is bound to the address we determined
// above and must be associated with an event loop, so we pass in a handle
// to our event loop. After the socket's created we inform that we're ready
// to go and start accepting connections.
let socket = TcpListener::bind(&addr)?;
println!("Listening on: {}", addr);
// Here we convert the `TcpListener` to a stream of incoming connections
// with the `incoming` method. We then define how to process each element in
// the stream with the `for_each` method.
//
// This combinator, defined on the `Stream` trait, will allow us to define a
// computation to happen for all items on the stream (in this case TCP
// connections made to the server). The return value of the `for_each`
// method is itself a future representing processing the entire stream of
// connections, and ends up being our server.
let done = socket
.incoming()
.map_err(|e| println!("failed to accept socket; error = {:?}", e))
.for_each(move |socket| {
// Once we're inside this closure this represents an accepted client
// from our server. The `socket` is the client connection (similar to
// how the standard library operates).
//
// We just want to copy all data read from the socket back onto the
// socket itself (e.g. "echo"). We can use the standard `io::copy`
// combinator in the `tokio-core` crate to do precisely this!
//
// The `copy` function takes two arguments, where to read from and where
// to write to. We only have one argument, though, with `socket`.
// Luckily there's a method, `Io::split`, which will split an Read/Write
// stream into its two halves. This operation allows us to work with
// each stream independently, such as pass them as two arguments to the
// `copy` function.
//
// The `copy` function then returns a future, and this future will be
// resolved when the copying operation is complete, resolving to the
// amount of data that was copied.
let (reader, writer) = socket.split();
let amt = io::copy(reader, writer);
// After our copy operation is complete we just print out some helpful
// information.
let msg = amt.then(move |result| {
match result {
Ok((amt, _, _)) => println!("wrote {} bytes", amt),
Err(e) => println!("error: {}", e),
}
Ok(())
});
// And this is where much of the magic of this server happens. We
// crucially want all clients to make progress concurrently, rather than
// blocking one on completion of another. To achieve this we use the
// `tokio::spawn` function to execute the work in the background.
//
// This function will transfer ownership of the future (`msg` in this
// case) to the Tokio runtime thread pool that. The thread pool will
// drive the future to completion.
//
// Essentially here we're executing a new task to run concurrently,
// which will allow all of our clients to be processed concurrently.
tokio::spawn(msg)
});
// And finally now that we've define what our server is, we run it!
//
// This starts the Tokio runtime, spawns the server task, and blocks the
// current thread until all tasks complete execution. Since the `done` task
// never completes (it just keeps accepting sockets), `tokio::run` blocks
// forever (until ctrl-c is pressed).
tokio::run(done);
Ok(())
}
|
