diff --git a/.cargo/config b/.cargo/config
new file mode 100644
index 0000000..6b77899
--- /dev/null
+++ b/.cargo/config
@@ -0,0 +1,2 @@
+[build]
+target = "wasm32-wasi"
diff --git a/Cargo.lock b/Cargo.lock
index ddc86b4..be46ae8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -11,6 +11,7 @@ name = "demo"
 version = "0.1.0"
 dependencies = [
  "getrandom",
+ "wasi-socket",
 ]
 
 [[package]]
@@ -35,3 +36,7 @@ name = "wasi"
 version = "0.9.0+wasi-snapshot-preview1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
+
+[[package]]
+name = "wasi-socket"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 3b64905..f71d89a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,3 +8,4 @@ edition = "2018"
 
 [dependencies]
 getrandom = "0.2"
+wasi-socket = { path = "socket-bindings" }
diff --git a/bundle/config.yaml b/bundle/config.yaml
new file mode 100644
index 0000000..bed25ab
--- /dev/null
+++ b/bundle/config.yaml
@@ -0,0 +1,6 @@
+---
+stdio:
+  stdin: "null"
+  stdout: "null"
+  stderr: "null"
+listen_address: "localhost:5000"
diff --git a/rust-toolchain b/rust-toolchain
new file mode 100644
index 0000000..bf867e0
--- /dev/null
+++ b/rust-toolchain
@@ -0,0 +1 @@
+nightly
diff --git a/socket-bindings/Cargo.toml b/socket-bindings/Cargo.toml
new file mode 100644
index 0000000..7d04ce7
--- /dev/null
+++ b/socket-bindings/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "wasi-socket"
+version = "0.1.0"
+authors = ["Daiki Ueno <dueno@redhat.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/socket-bindings/src/error.rs b/socket-bindings/src/error.rs
new file mode 100644
index 0000000..e642e0d
--- /dev/null
+++ b/socket-bindings/src/error.rs
@@ -0,0 +1,47 @@
+use super::Errno;
+use core::fmt;
+use core::num::NonZeroU16;
+use crate::strerror;
+
+/// A raw error returned by wasi-socket APIs, internally containing a 16-bit
+/// error code.
+#[derive(Copy, Clone, PartialEq, Eq, Ord, PartialOrd)]
+pub struct Error {
+    code: NonZeroU16,
+}
+
+impl Error {
+    /// Constructs a new error from a raw error code, returning `None` if the
+    /// error code is zero (which means success).
+    pub fn from_raw_error(error: Errno) -> Option<Error> {
+        Some(Error {
+            code: NonZeroU16::new(error)?,
+        })
+    }
+
+    /// Returns the raw error code that this error represents.
+    pub fn raw_error(&self) -> u16 {
+        self.code.get()
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{} (error {})", strerror(self.code.get()), self.code)?;
+        Ok(())
+    }
+}
+
+impl fmt::Debug for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Error")
+            .field("code", &self.code)
+            .field("message", &strerror(self.code.get()))
+            .finish()
+    }
+}
+
+#[cfg(feature = "std")]
+extern crate std;
+#[cfg(feature = "std")]
+impl std::error::Error for Error {}
diff --git a/socket-bindings/src/generated.rs b/socket-bindings/src/generated.rs
new file mode 100644
index 0000000..d91a88f
--- /dev/null
+++ b/socket-bindings/src/generated.rs
@@ -0,0 +1,269 @@
+// This file is automatically generated, DO NOT EDIT
+//
+// To regenerate this file run the `crates/witx-bindgen` command
+
+use core::mem::MaybeUninit;
+
+pub use crate::error::Error;
+pub type Result<T, E = Error> = core::result::Result<T, E>;
+pub type Errno = u16;
+/// No error occurred. System call completed successfully.
+pub const ERRNO_SUCCESS: Errno = 0;
+/// Argument list too long.
+pub const ERRNO_2BIG: Errno = 1;
+/// Permission denied.
+pub const ERRNO_ACCESS: Errno = 2;
+/// Address in use.
+pub const ERRNO_ADDRINUSE: Errno = 3;
+/// Address not available.
+pub const ERRNO_ADDRNOTAVAIL: Errno = 4;
+/// Address family not supported.
+pub const ERRNO_AFNOSUPPORT: Errno = 5;
+/// Resource unavailable, or operation would block.
+pub const ERRNO_AGAIN: Errno = 6;
+/// Connection already in progress.
+pub const ERRNO_ALREADY: Errno = 7;
+/// Bad file descriptor.
+pub const ERRNO_BADF: Errno = 8;
+/// Bad message.
+pub const ERRNO_BADMSG: Errno = 9;
+/// Device or resource busy.
+pub const ERRNO_BUSY: Errno = 10;
+/// Operation canceled.
+pub const ERRNO_CANCELED: Errno = 11;
+/// No child processes.
+pub const ERRNO_CHILD: Errno = 12;
+/// Connection aborted.
+pub const ERRNO_CONNABORTED: Errno = 13;
+/// Connection refused.
+pub const ERRNO_CONNREFUSED: Errno = 14;
+/// Connection reset.
+pub const ERRNO_CONNRESET: Errno = 15;
+/// Resource deadlock would occur.
+pub const ERRNO_DEADLK: Errno = 16;
+/// Destination address required.
+pub const ERRNO_DESTADDRREQ: Errno = 17;
+/// Mathematics argument out of domain of function.
+pub const ERRNO_DOM: Errno = 18;
+/// Reserved.
+pub const ERRNO_DQUOT: Errno = 19;
+/// File exists.
+pub const ERRNO_EXIST: Errno = 20;
+/// Bad address.
+pub const ERRNO_FAULT: Errno = 21;
+/// File too large.
+pub const ERRNO_FBIG: Errno = 22;
+/// Host is unreachable.
+pub const ERRNO_HOSTUNREACH: Errno = 23;
+/// Identifier removed.
+pub const ERRNO_IDRM: Errno = 24;
+/// Illegal byte sequence.
+pub const ERRNO_ILSEQ: Errno = 25;
+/// Operation in progress.
+pub const ERRNO_INPROGRESS: Errno = 26;
+/// Interrupted function.
+pub const ERRNO_INTR: Errno = 27;
+/// Invalid argument.
+pub const ERRNO_INVAL: Errno = 28;
+/// I/O error.
+pub const ERRNO_IO: Errno = 29;
+/// Socket is connected.
+pub const ERRNO_ISCONN: Errno = 30;
+/// Is a directory.
+pub const ERRNO_ISDIR: Errno = 31;
+/// Too many levels of symbolic links.
+pub const ERRNO_LOOP: Errno = 32;
+/// File descriptor value too large.
+pub const ERRNO_MFILE: Errno = 33;
+/// Too many links.
+pub const ERRNO_MLINK: Errno = 34;
+/// Message too large.
+pub const ERRNO_MSGSIZE: Errno = 35;
+/// Reserved.
+pub const ERRNO_MULTIHOP: Errno = 36;
+/// Filename too long.
+pub const ERRNO_NAMETOOLONG: Errno = 37;
+/// Network is down.
+pub const ERRNO_NETDOWN: Errno = 38;
+/// Connection aborted by network.
+pub const ERRNO_NETRESET: Errno = 39;
+/// Network unreachable.
+pub const ERRNO_NETUNREACH: Errno = 40;
+/// Too many files open in system.
+pub const ERRNO_NFILE: Errno = 41;
+/// No buffer space available.
+pub const ERRNO_NOBUFS: Errno = 42;
+/// No such device.
+pub const ERRNO_NODEV: Errno = 43;
+/// No such file or directory.
+pub const ERRNO_NOENT: Errno = 44;
+/// Executable file format error.
+pub const ERRNO_NOEXEC: Errno = 45;
+/// No locks available.
+pub const ERRNO_NOLCK: Errno = 46;
+/// Reserved.
+pub const ERRNO_NOLINK: Errno = 47;
+/// Not enough space.
+pub const ERRNO_NOMEM: Errno = 48;
+/// No message of the desired type.
+pub const ERRNO_NOMSG: Errno = 49;
+/// Protocol not available.
+pub const ERRNO_NOPROTOOPT: Errno = 50;
+/// No space left on device.
+pub const ERRNO_NOSPC: Errno = 51;
+/// Function not supported.
+pub const ERRNO_NOSYS: Errno = 52;
+/// The socket is not connected.
+pub const ERRNO_NOTCONN: Errno = 53;
+/// Not a directory or a symbolic link to a directory.
+pub const ERRNO_NOTDIR: Errno = 54;
+/// Directory not empty.
+pub const ERRNO_NOTEMPTY: Errno = 55;
+/// State not recoverable.
+pub const ERRNO_NOTRECOVERABLE: Errno = 56;
+/// Not a socket.
+pub const ERRNO_NOTSOCK: Errno = 57;
+/// Not supported, or operation not supported on socket.
+pub const ERRNO_NOTSUP: Errno = 58;
+/// Inappropriate I/O control operation.
+pub const ERRNO_NOTTY: Errno = 59;
+/// No such device or address.
+pub const ERRNO_NXIO: Errno = 60;
+/// Value too large to be stored in data type.
+pub const ERRNO_OVERFLOW: Errno = 61;
+/// Previous owner died.
+pub const ERRNO_OWNERDEAD: Errno = 62;
+/// Operation not permitted.
+pub const ERRNO_PERM: Errno = 63;
+/// Broken pipe.
+pub const ERRNO_PIPE: Errno = 64;
+/// Protocol error.
+pub const ERRNO_PROTO: Errno = 65;
+/// Protocol not supported.
+pub const ERRNO_PROTONOSUPPORT: Errno = 66;
+/// Protocol wrong type for socket.
+pub const ERRNO_PROTOTYPE: Errno = 67;
+/// Result too large.
+pub const ERRNO_RANGE: Errno = 68;
+/// Read-only file system.
+pub const ERRNO_ROFS: Errno = 69;
+/// Invalid seek.
+pub const ERRNO_SPIPE: Errno = 70;
+/// No such process.
+pub const ERRNO_SRCH: Errno = 71;
+/// Reserved.
+pub const ERRNO_STALE: Errno = 72;
+/// Connection timed out.
+pub const ERRNO_TIMEDOUT: Errno = 73;
+/// Text file busy.
+pub const ERRNO_TXTBSY: Errno = 74;
+/// Cross-device link.
+pub const ERRNO_XDEV: Errno = 75;
+/// Extension: Capabilities insufficient.
+pub const ERRNO_NOTCAPABLE: Errno = 76;
+pub(crate) fn strerror(code: u16) -> &'static str {
+    match code {
+        ERRNO_SUCCESS => "No error occurred. System call completed successfully.",
+        ERRNO_2BIG => "Argument list too long.",
+        ERRNO_ACCESS => "Permission denied.",
+        ERRNO_ADDRINUSE => "Address in use.",
+        ERRNO_ADDRNOTAVAIL => "Address not available.",
+        ERRNO_AFNOSUPPORT => "Address family not supported.",
+        ERRNO_AGAIN => "Resource unavailable, or operation would block.",
+        ERRNO_ALREADY => "Connection already in progress.",
+        ERRNO_BADF => "Bad file descriptor.",
+        ERRNO_BADMSG => "Bad message.",
+        ERRNO_BUSY => "Device or resource busy.",
+        ERRNO_CANCELED => "Operation canceled.",
+        ERRNO_CHILD => "No child processes.",
+        ERRNO_CONNABORTED => "Connection aborted.",
+        ERRNO_CONNREFUSED => "Connection refused.",
+        ERRNO_CONNRESET => "Connection reset.",
+        ERRNO_DEADLK => "Resource deadlock would occur.",
+        ERRNO_DESTADDRREQ => "Destination address required.",
+        ERRNO_DOM => "Mathematics argument out of domain of function.",
+        ERRNO_DQUOT => "Reserved.",
+        ERRNO_EXIST => "File exists.",
+        ERRNO_FAULT => "Bad address.",
+        ERRNO_FBIG => "File too large.",
+        ERRNO_HOSTUNREACH => "Host is unreachable.",
+        ERRNO_IDRM => "Identifier removed.",
+        ERRNO_ILSEQ => "Illegal byte sequence.",
+        ERRNO_INPROGRESS => "Operation in progress.",
+        ERRNO_INTR => "Interrupted function.",
+        ERRNO_INVAL => "Invalid argument.",
+        ERRNO_IO => "I/O error.",
+        ERRNO_ISCONN => "Socket is connected.",
+        ERRNO_ISDIR => "Is a directory.",
+        ERRNO_LOOP => "Too many levels of symbolic links.",
+        ERRNO_MFILE => "File descriptor value too large.",
+        ERRNO_MLINK => "Too many links.",
+        ERRNO_MSGSIZE => "Message too large.",
+        ERRNO_MULTIHOP => "Reserved.",
+        ERRNO_NAMETOOLONG => "Filename too long.",
+        ERRNO_NETDOWN => "Network is down.",
+        ERRNO_NETRESET => "Connection aborted by network.",
+        ERRNO_NETUNREACH => "Network unreachable.",
+        ERRNO_NFILE => "Too many files open in system.",
+        ERRNO_NOBUFS => "No buffer space available.",
+        ERRNO_NODEV => "No such device.",
+        ERRNO_NOENT => "No such file or directory.",
+        ERRNO_NOEXEC => "Executable file format error.",
+        ERRNO_NOLCK => "No locks available.",
+        ERRNO_NOLINK => "Reserved.",
+        ERRNO_NOMEM => "Not enough space.",
+        ERRNO_NOMSG => "No message of the desired type.",
+        ERRNO_NOPROTOOPT => "Protocol not available.",
+        ERRNO_NOSPC => "No space left on device.",
+        ERRNO_NOSYS => "Function not supported.",
+        ERRNO_NOTCONN => "The socket is not connected.",
+        ERRNO_NOTDIR => "Not a directory or a symbolic link to a directory.",
+        ERRNO_NOTEMPTY => "Directory not empty.",
+        ERRNO_NOTRECOVERABLE => "State not recoverable.",
+        ERRNO_NOTSOCK => "Not a socket.",
+        ERRNO_NOTSUP => "Not supported, or operation not supported on socket.",
+        ERRNO_NOTTY => "Inappropriate I/O control operation.",
+        ERRNO_NXIO => "No such device or address.",
+        ERRNO_OVERFLOW => "Value too large to be stored in data type.",
+        ERRNO_OWNERDEAD => "Previous owner died.",
+        ERRNO_PERM => "Operation not permitted.",
+        ERRNO_PIPE => "Broken pipe.",
+        ERRNO_PROTO => "Protocol error.",
+        ERRNO_PROTONOSUPPORT => "Protocol not supported.",
+        ERRNO_PROTOTYPE => "Protocol wrong type for socket.",
+        ERRNO_RANGE => "Result too large.",
+        ERRNO_ROFS => "Read-only file system.",
+        ERRNO_SPIPE => "Invalid seek.",
+        ERRNO_SRCH => "No such process.",
+        ERRNO_STALE => "Reserved.",
+        ERRNO_TIMEDOUT => "Connection timed out.",
+        ERRNO_TXTBSY => "Text file busy.",
+        ERRNO_XDEV => "Cross-device link.",
+        ERRNO_NOTCAPABLE => "Extension: Capabilities insufficient.",
+        _ => "Unknown error.",
+    }
+}
+pub type Fd = u32;
+/// Accept an incoming connection.
+///
+/// ## Return
+///
+/// * `opened_fd` - The file descriptor that has been opened.
+pub unsafe fn accept() -> Result<Fd> {
+    let mut opened_fd = MaybeUninit::uninit();
+    let rc = wasi_ephemeral_socket::accept(opened_fd.as_mut_ptr());
+    if let Some(err) = Error::from_raw_error(rc) {
+        Err(err)
+    } else {
+        Ok(opened_fd.assume_init())
+    }
+}
+
+pub mod wasi_ephemeral_socket {
+    use super::*;
+    #[link(wasm_import_module = "wasi_ephemeral_socket")]
+    extern "C" {
+        /// Accept an incoming connection.
+        pub fn accept(opened_fd: *mut Fd) -> Errno;
+    }
+}
diff --git a/socket-bindings/src/lib.rs b/socket-bindings/src/lib.rs
new file mode 100644
index 0000000..86fdcd0
--- /dev/null
+++ b/socket-bindings/src/lib.rs
@@ -0,0 +1,3 @@
+mod error;
+mod generated;
+pub use generated::*;
diff --git a/src/main.rs b/src/main.rs
index 87e14ba..fab2cb9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,8 @@
+#![feature(wasi_ext)]
+
 use std::ffi::CString;
-use std::io::Read;
+use std::io::prelude::*;
+use std::os::wasi::prelude::*;
 
 fn main() {
     let mut buf = [0u8; 4];
@@ -7,8 +10,10 @@ fn main() {
     let number = u32::from_le_bytes(buf);
     let string = CString::new(format!("=={:08x}==", number)).unwrap();
 
-    println!("Press ENTER to reveal the secret...");
-    std::io::stdin().read_exact(&mut [0u8]).unwrap();
+    let socket_fd = unsafe { wasi_socket::accept().unwrap() };
+    let mut socket = unsafe { std::fs::File::from_raw_fd(socket_fd) };
 
-    println!("The secret is: {:?}", string);
+    socket.write_all(b"Press ENTER to reveal the secret...\n").unwrap();
+    socket.read_exact(&mut [0u8]).unwrap();
+    socket.write_all(format!("The secret is: {:?}\n", string).as_bytes()).unwrap();
 }