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
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
use crate::io::{Interest, PollEvented};
use crate::net::tcp::TcpStream;

cfg_not_wasi! {
    use crate::net::{to_socket_addrs, ToSocketAddrs};
}

use std::fmt;
use std::io;
use std::net::{self, SocketAddr};
use std::task::{Context, Poll};

cfg_net! {
    /// A TCP socket server, listening for connections.
    ///
    /// You can accept a new connection by using the [`accept`](`TcpListener::accept`)
    /// method.
    ///
    /// A `TcpListener` can be turned into a `Stream` with [`TcpListenerStream`].
    ///
    /// [`TcpListenerStream`]: https://docs.rs/tokio-stream/0.1/tokio_stream/wrappers/struct.TcpListenerStream.html
    ///
    /// # Errors
    ///
    /// Note that accepting a connection can lead to various errors and not all
    /// of them are necessarily fatal ‒ for example having too many open file
    /// descriptors or the other side closing the connection while it waits in
    /// an accept queue. These would terminate the stream if not handled in any
    /// way.
    ///
    /// # Examples
    ///
    /// Using `accept`:
    /// ```no_run
    /// use tokio::net::TcpListener;
    ///
    /// use std::io;
    ///
    /// async fn process_socket<T>(socket: T) {
    ///     # drop(socket);
    ///     // do work with socket here
    /// }
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let listener = TcpListener::bind("127.0.0.1:8080").await?;
    ///
    ///     loop {
    ///         let (socket, _) = listener.accept().await?;
    ///         process_socket(socket).await;
    ///     }
    /// }
    /// ```
    pub struct TcpListener {
        io: PollEvented<mio::net::TcpListener>,
    }
}

impl TcpListener {
    cfg_not_wasi! {
        /// Creates a new TcpListener, which will be bound to the specified address.
        ///
        /// The returned listener is ready for accepting connections.
        ///
        /// Binding with a port number of 0 will request that the OS assigns a port
        /// to this listener. The port allocated can be queried via the `local_addr`
        /// method.
        ///
        /// The address type can be any implementor of the [`ToSocketAddrs`] trait.
        /// If `addr` yields multiple addresses, bind will be attempted with each of
        /// the addresses until one succeeds and returns the listener. If none of
        /// the addresses succeed in creating a listener, the error returned from
        /// the last attempt (the last address) is returned.
        ///
        /// This function sets the `SO_REUSEADDR` option on the socket.
        ///
        /// To configure the socket before binding, you can use the [`TcpSocket`]
        /// type.
        ///
        /// [`ToSocketAddrs`]: trait@crate::net::ToSocketAddrs
        /// [`TcpSocket`]: struct@crate::net::TcpSocket
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::net::TcpListener;
        ///
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let listener = TcpListener::bind("127.0.0.1:2345").await?;
        ///
        ///     // use the listener
        ///
        ///     # let _ = listener;
        ///     Ok(())
        /// }
        /// ```
        pub async fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
            let addrs = to_socket_addrs(addr).await?;

            let mut last_err = None;

            for addr in addrs {
                match TcpListener::bind_addr(addr) {
                    Ok(listener) => return Ok(listener),
                    Err(e) => last_err = Some(e),
                }
            }

            Err(last_err.unwrap_or_else(|| {
                io::Error::new(
                    io::ErrorKind::InvalidInput,
                    "could not resolve to any address",
                )
            }))
        }

        fn bind_addr(addr: SocketAddr) -> io::Result<TcpListener> {
            let listener = mio::net::TcpListener::bind(addr)?;
            TcpListener::new(listener)
        }
    }

    /// Accepts a new incoming connection from this listener.
    ///
    /// This function will yield once a new TCP connection is established. When
    /// established, the corresponding [`TcpStream`] and the remote peer's
    /// address will be returned.
    ///
    /// # Cancel safety
    ///
    /// This method is cancel safe. If the method is used as the event in a
    /// [`tokio::select!`](crate::select) statement and some other branch
    /// completes first, then it is guaranteed that no new connections were
    /// accepted by this method.
    ///
    /// [`TcpStream`]: struct@crate::net::TcpStream
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use tokio::net::TcpListener;
    ///
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let listener = TcpListener::bind("127.0.0.1:8080").await?;
    ///
    ///     match listener.accept().await {
    ///         Ok((_socket, addr)) => println!("new client: {:?}", addr),
    ///         Err(e) => println!("couldn't get client: {:?}", e),
    ///     }
    ///
    ///     Ok(())
    /// }
    /// ```
    pub async fn accept(&self) -> io::Result<(TcpStream, SocketAddr)> {
        let (mio, addr) = self
            .io
            .registration()
            .async_io(Interest::READABLE, || self.io.accept())
            .await?;

        let stream = TcpStream::new(mio)?;
        Ok((stream, addr))
    }

    /// Polls to accept a new incoming connection to this listener.
    ///
    /// If there is no connection to accept, `Poll::Pending` is returned and the
    /// current task will be notified by a waker.  Note that on multiple calls
    /// to `poll_accept`, only the `Waker` from the `Context` passed to the most
    /// recent call is scheduled to receive a wakeup.
    pub fn poll_accept(&self, cx: &mut Context<'_>) -> Poll<io::Result<(TcpStream, SocketAddr)>> {
        loop {
            let ev = ready!(self.io.registration().poll_read_ready(cx))?;

            match self.io.accept() {
                Ok((io, addr)) => {
                    let io = TcpStream::new(io)?;
                    return Poll::Ready(Ok((io, addr)));
                }
                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                    self.io.registration().clear_readiness(ev);
                }
                Err(e) => return Poll::Ready(Err(e)),
            }
        }
    }

    /// Creates new `TcpListener` from a `std::net::TcpListener`.
    ///
    /// This function is intended to be used to wrap a TCP listener from the
    /// standard library in the Tokio equivalent.
    ///
    /// This API is typically paired with the `socket2` crate and the `Socket`
    /// type to build up and customize a listener before it's shipped off to the
    /// backing event loop. This allows configuration of options like
    /// `SO_REUSEPORT`, binding to multiple addresses, etc.
    ///
    /// # Notes
    ///
    /// The caller is responsible for ensuring that the listener is in
    /// non-blocking mode. Otherwise all I/O operations on the listener
    /// will block the thread, which will cause unexpected behavior.
    /// Non-blocking mode can be set using [`set_nonblocking`].
    ///
    /// [`set_nonblocking`]: std::net::TcpListener::set_nonblocking
    ///
    /// # Examples
    ///
    /// ```rust,no_run
    /// use std::error::Error;
    /// use tokio::net::TcpListener;
    ///
    /// #[tokio::main]
    /// async fn main() -> Result<(), Box<dyn Error>> {
    ///     let std_listener = std::net::TcpListener::bind("127.0.0.1:0")?;
    ///     std_listener.set_nonblocking(true)?;
    ///     let listener = TcpListener::from_std(std_listener)?;
    ///     Ok(())
    /// }
    /// ```
    ///
    /// # Panics
    ///
    /// This function panics if it is not called from within a runtime with
    /// IO enabled.
    ///
    /// The runtime is usually set implicitly when this function is called
    /// from a future driven by a tokio runtime, otherwise runtime can be set
    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
    #[track_caller]
    pub fn from_std(listener: net::TcpListener) -> io::Result<TcpListener> {
        let io = mio::net::TcpListener::from_std(listener);
        let io = PollEvented::new(io)?;
        Ok(TcpListener { io })
    }

    /// Turns a [`tokio::net::TcpListener`] into a [`std::net::TcpListener`].
    ///
    /// The returned [`std::net::TcpListener`] will have nonblocking mode set as
    /// `true`.  Use [`set_nonblocking`] to change the blocking mode if needed.
    ///
    /// # Examples
    ///
    /// ```rust,no_run
    /// use std::error::Error;
    ///
    /// #[tokio::main]
    /// async fn main() -> Result<(), Box<dyn Error>> {
    ///     let tokio_listener = tokio::net::TcpListener::bind("127.0.0.1:0").await?;
    ///     let std_listener = tokio_listener.into_std()?;
    ///     std_listener.set_nonblocking(false)?;
    ///     Ok(())
    /// }
    /// ```
    ///
    /// [`tokio::net::TcpListener`]: TcpListener
    /// [`std::net::TcpListener`]: std::net::TcpListener
    /// [`set_nonblocking`]: fn@std::net::TcpListener::set_nonblocking
    pub fn into_std(self) -> io::Result<std::net::TcpListener> {
        #[cfg(unix)]
        {
            use std::os::unix::io::{FromRawFd, IntoRawFd};
            self.io
                .into_inner()
                .map(|io| io.into_raw_fd())
                .map(|raw_fd| unsafe { std::net::TcpListener::from_raw_fd(raw_fd) })
        }

        #[cfg(windows)]
        {
            use std::os::windows::io::{FromRawSocket, IntoRawSocket};
            self.io
                .into_inner()
                .map(|io| io.into_raw_socket())
                .map(|raw_socket| unsafe { std::net::TcpListener::from_raw_socket(raw_socket) })
        }

        #[cfg(target_os = "wasi")]
        {
            use std::os::wasi::io::{FromRawFd, IntoRawFd};
            self.io
                .into_inner()
                .map(|io| io.into_raw_fd())
                .map(|raw_fd| unsafe { std::net::TcpListener::from_raw_fd(raw_fd) })
        }
    }

    cfg_not_wasi! {
        pub(crate) fn new(listener: mio::net::TcpListener) -> io::Result<TcpListener> {
            let io = PollEvented::new(listener)?;
            Ok(TcpListener { io })
        }
    }

    /// Returns the local address that this listener is bound to.
    ///
    /// This can be useful, for example, when binding to port 0 to figure out
    /// which port was actually bound.
    ///
    /// # Examples
    ///
    /// ```rust,no_run
    /// use tokio::net::TcpListener;
    ///
    /// use std::io;
    /// use std::net::{Ipv4Addr, SocketAddr, SocketAddrV4};
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let listener = TcpListener::bind("127.0.0.1:8080").await?;
    ///
    ///     assert_eq!(listener.local_addr()?,
    ///                SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080)));
    ///
    ///     Ok(())
    /// }
    /// ```
    pub fn local_addr(&self) -> io::Result<SocketAddr> {
        self.io.local_addr()
    }

    /// Gets the value of the `IP_TTL` option for this socket.
    ///
    /// For more information about this option, see [`set_ttl`].
    ///
    /// [`set_ttl`]: method@Self::set_ttl
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use tokio::net::TcpListener;
    ///
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///    let listener = TcpListener::bind("127.0.0.1:0").await?;
    ///
    ///    listener.set_ttl(100).expect("could not set TTL");
    ///    assert_eq!(listener.ttl()?, 100);
    ///
    ///    Ok(())
    /// }
    /// ```
    pub fn ttl(&self) -> io::Result<u32> {
        self.io.ttl()
    }

    /// Sets the value for the `IP_TTL` option on this socket.
    ///
    /// This value sets the time-to-live field that is used in every packet sent
    /// from this socket.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use tokio::net::TcpListener;
    ///
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let listener = TcpListener::bind("127.0.0.1:0").await?;
    ///
    ///     listener.set_ttl(100).expect("could not set TTL");
    ///
    ///     Ok(())
    /// }
    /// ```
    pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
        self.io.set_ttl(ttl)
    }
}

impl TryFrom<net::TcpListener> for TcpListener {
    type Error = io::Error;

    /// Consumes stream, returning the tokio I/O object.
    ///
    /// This is equivalent to
    /// [`TcpListener::from_std(stream)`](TcpListener::from_std).
    fn try_from(stream: net::TcpListener) -> Result<Self, Self::Error> {
        Self::from_std(stream)
    }
}

impl fmt::Debug for TcpListener {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.io.fmt(f)
    }
}

#[cfg(unix)]
mod sys {
    use super::TcpListener;
    use std::os::unix::prelude::*;

    impl AsRawFd for TcpListener {
        fn as_raw_fd(&self) -> RawFd {
            self.io.as_raw_fd()
        }
    }

    impl AsFd for TcpListener {
        fn as_fd(&self) -> BorrowedFd<'_> {
            unsafe { BorrowedFd::borrow_raw(self.as_raw_fd()) }
        }
    }
}

cfg_unstable! {
    #[cfg(target_os = "wasi")]
    mod sys {
        use super::TcpListener;
        use std::os::wasi::prelude::*;

        impl AsRawFd for TcpListener {
            fn as_raw_fd(&self) -> RawFd {
                self.io.as_raw_fd()
            }
        }

        impl AsFd for TcpListener {
            fn as_fd(&self) -> BorrowedFd<'_> {
                unsafe { BorrowedFd::borrow_raw(self.as_raw_fd()) }
            }
        }
    }
}

cfg_windows! {
    use crate::os::windows::io::{AsRawSocket, RawSocket, AsSocket, BorrowedSocket};

    impl AsRawSocket for TcpListener {
        fn as_raw_socket(&self) -> RawSocket {
            self.io.as_raw_socket()
        }
    }

    impl AsSocket for TcpListener {
        fn as_socket(&self) -> BorrowedSocket<'_> {
            unsafe { BorrowedSocket::borrow_raw(self.as_raw_socket()) }
        }
    }
}