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Diffstat (limited to 'third_party/rust/tokio-0.1.22/examples/echo.rs')
| -rw-r--r-- | third_party/rust/tokio-0.1.22/examples/echo.rs | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/third_party/rust/tokio-0.1.22/examples/echo.rs b/third_party/rust/tokio-0.1.22/examples/echo.rs new file mode 100644 index 0000000000..45f808f89d --- /dev/null +++ b/third_party/rust/tokio-0.1.22/examples/echo.rs @@ -0,0 +1,115 @@ +//! 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(()) +} |