some api adjustments

src/address.rs

@@ -1,7 +1,7 @@
 use std::net::SocketAddr;
 
 /// An address type, for use with the [`Socket`](`crate::Socket`) trait.
-pub trait Address: Clone {
+pub trait Address: Sized + Clone {
     /// Are the two addresses the same host?
     ///
     /// For IP based addresses, this checks if the IP of two addresses are the same.

src/error.rs

@@ -12,6 +12,9 @@ pub enum Error {
     /// Failed to send.
     #[error("Failed to send.")]
     FailedToSend,
+    /// Failed to receive.
+    #[error("Failed to receive.")]
+    FailedToReceive,
     /// A bad parameter was passed to the function.
     #[error("A bad parameter was passed to the function.")]
     BadParameter,

src/host.rs

@@ -182,6 +182,11 @@ impl<S: Socket> Host<S> {
         }
     }
 
+    /// Get the maximum number of peers that can connect to this host.
+    pub fn peer_limit(&self) -> usize {
+        self.peers.len()
+    }
+
     /// Get a reference to a single peer.
     ///
     /// # Note

src/socket.rs

@@ -23,7 +23,7 @@ pub trait Socket: Sized {
     ///
     /// An example is the standard library's [`std::net::SocketAddr`], used with
     /// [`std::net::UdpSocket`].
-    type PeerAddress: Address;
+    type PeerAddress: Address + 'static;
     /// Errors returned by this socket.
     type Error: std::error::Error + Send + Sync + 'static;