diff --git a/proto/src/peer/mod.rs b/proto/src/peer/mod.rs
index ca31c63..e81126b 100644
--- a/proto/src/peer/mod.rs
+++ b/proto/src/peer/mod.rs
@@ -1,3 +1,5 @@
 mod message;
+mod worker;
 
 pub use self::message::*;
+pub use self::worker::*;
diff --git a/proto/src/peer/worker.rs b/proto/src/peer/worker.rs
new file mode 100644
index 0000000..6cca3c0
--- /dev/null
+++ b/proto/src/peer/worker.rs
@@ -0,0 +1,152 @@
+//! Defines a worker model for peer connections.
+
+use std::io;
+use std::net::SocketAddr;
+
+use thiserror::Error;
+use tokio::net::TcpStream;
+
+use crate::core::{FrameReader, FrameWriter, Worker};
+use crate::peer::{Message, PeerConnectionType, PeerInit};
+
+// Peer states:
+//
+//  - closed
+//  - open
+//  - waiting for pierce firewall
+//  - cannot connect
+//
+// Transitions:
+//
+//  - closed:
+//    -> open:
+//         connect
+//         send peerinit
+//    -> waiting for pierce firewall:
+//         connect failed, or send peerinit failed
+//         send connecttopeer to server
+//    -> open:
+//         accept connection
+//         receive peerinit
+//  - open:
+//    -> closed:
+//         connection closed
+//  - waiting for pierce firewall:
+//    -> open:
+//         accept connection
+//         receive pierce firewall
+//         ???send peer init???
+//    -> cannot connect:
+//         receive cannot connect
+//
+
+/// A peer to connect to.
+#[derive(Debug)]
+pub struct PeerConnection {
+  /// The address of the peer.
+  pub address: SocketAddr,
+
+  /// The type of connection to establish.
+  pub connection_type: PeerConnectionType,
+
+  /// The user name as which to identify ourselves to the peer.
+  pub our_user_name: String,
+}
+
+/// An error that arose while establishing a connection to a peer.
+#[derive(Debug, Error)]
+pub enum PeerConnectionError {
+  #[error("error establishing network connection: {0}")]
+  ConnectError(#[source] io::Error),
+
+  #[error("error sending initial message: {0}")]
+  WriteError(#[source] io::Error),
+}
+
+/// A `Worker` that handles an open connection to a peer.
+type PeerWorker = Worker<Message, Message>;
+
+impl PeerConnection {
+  pub async fn connect(self) -> Result<PeerWorker, PeerConnectionError> {
+    let stream = TcpStream::connect(self.address)
+      .await
+      .map_err(PeerConnectionError::ConnectError)?;
+
+    let (read_half, write_half) = stream.into_split();
+    let reader = FrameReader::new(read_half);
+    let mut writer = FrameWriter::new(write_half);
+
+    writer
+      .write(&Message::PeerInit(PeerInit {
+        user_name: self.our_user_name,
+        connection_type: self.connection_type,
+        token: 0,
+      }))
+      .await
+      .map_err(PeerConnectionError::WriteError)?;
+
+    Ok(Worker::from_parts(reader, writer))
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use std::net::{Ipv4Addr, SocketAddr, SocketAddrV4};
+
+  use tokio::net::TcpListener;
+
+  use crate::core::FrameReader;
+  use crate::peer::{Message, PeerConnectionType, PeerInit};
+
+  use super::{PeerConnection, PeerConnectionError};
+
+  #[tokio::test]
+  async fn peer_connection_connect_error() {
+    let connection = PeerConnection {
+      address: SocketAddr::V4(SocketAddrV4::new(
+        // TODO: use example IP instead, ensuring this fails.
+        Ipv4Addr::new(0, 0, 0, 1),
+        42,
+      )),
+      connection_type: PeerConnectionType::File,
+      our_user_name: "me".to_string(),
+    };
+
+    let err = connection.connect().await.unwrap_err();
+
+    match err {
+      PeerConnectionError::ConnectError(_) => (),
+      _ => panic!("Wrong error: {:?}", err),
+    }
+  }
+
+  #[tokio::test]
+  async fn peer_connection_success() {
+    let listener = TcpListener::bind("localhost:0")
+      .await
+      .expect("binding listener");
+    let address = listener.local_addr().expect("getting local address");
+
+    let connection = PeerConnection {
+      address,
+      connection_type: PeerConnectionType::File,
+      our_user_name: "me".to_string(),
+    };
+
+    let (connect_result, accept_result) =
+      tokio::join!(connection.connect(), listener.accept());
+
+    let _worker = connect_result.expect("connecting");
+    let (stream, _remote_address) = accept_result.expect("accepting");
+
+    let message = FrameReader::new(stream).read().await.expect("reading");
+    assert_eq!(
+      message,
+      Some(Message::PeerInit(PeerInit {
+        user_name: "me".to_string(),
+        connection_type: PeerConnectionType::File,
+        token: 0,
+      }))
+    );
+  }
+}