diff --git a/server/src/session/mod.rs b/server/src/session/mod.rs
index 0b4af65..e5c7cb0 100644
--- a/server/src/session/mod.rs
+++ b/server/src/session/mod.rs
@@ -71,7 +71,7 @@ impl transport::App for Session {
         self.streams.poll(conn);
 
         // Fetch the next media fragment, possibly queuing up stream data.
-        self.poll_source(conn, session).expect("poll_source");
+        self.poll_source(conn, session)?;
 
         Ok(())
     }
diff --git a/server/src/transport/server.rs b/server/src/transport/server.rs
index d0ab1f7..19031af 100644
--- a/server/src/transport/server.rs
+++ b/server/src/transport/server.rs
@@ -151,7 +151,6 @@ impl<T: app::App> Server<T> {
 
             // Check if it's an existing connection.
             if let Some(conn) = self.conns.get_mut(&hdr.dcid) {
-                // initial or handshake traffic.
                 conn.quiche.recv(src, info)?;
 
                 if conn.session.is_none() && conn.quiche.is_established() {
@@ -162,7 +161,6 @@ impl<T: app::App> Server<T> {
 
                 continue;
             } else if let Some(conn) = self.conns.get_mut(&conn_id) {
-                // 1-RTT traffic.
                 conn.quiche.recv(src, info)?;
 
                 // TODO is this needed here?
@@ -176,7 +174,8 @@ impl<T: app::App> Server<T> {
             }
 
             if hdr.ty != quiche::Type::Initial {
-                anyhow::bail!("unknown connection ID");
+                log::warn!("unknown connection ID");
+                continue;
             }
 
             let mut dst = [0; MAX_DATAGRAM_SIZE];
@@ -222,11 +221,13 @@ impl<T: app::App> Server<T> {
             // The token was not valid, meaning the retry failed, so
             // drop the packet.
             if odcid.is_none() {
-                anyhow::bail!("invalid token");
+                log::warn!("invalid token");
+                continue;
             }
 
             if scid.len() != hdr.dcid.len() {
-                anyhow::bail!("invalid connection ID");
+                log::warn!("invalid connection ID");
+                continue;
             }
 
             // Reuse the source connection ID we sent in the Retry packet,
@@ -234,6 +235,8 @@ impl<T: app::App> Server<T> {
             let conn_id = hdr.dcid.clone();
             let local_addr = self.socket.local_addr().unwrap();
 
+            log::debug!("new connection: dcid={:?} scid={:?}", hdr.dcid, scid);
+
             let mut conn =
                 quiche::accept(&conn_id, odcid.as_ref(), local_addr, from, &mut self.quic)?;
 
@@ -246,13 +249,16 @@ impl<T: app::App> Server<T> {
                 app: T::default(),
             };
 
-            self.conns
-                .insert(user.quiche.source_id().into_owned(), user);
+            self.conns.insert(conn_id, user);
         }
     }
 
     pub fn app(&mut self) -> anyhow::Result<()> {
         for conn in self.conns.values_mut() {
+            if conn.quiche.is_closed() {
+                continue;
+            }
+
             if let Some(session) = &mut conn.session {
                 if let Err(e) = conn.app.poll(&mut conn.quiche, session) {
                     log::debug!("app error: {:?}", e);
@@ -271,23 +277,12 @@ impl<T: app::App> Server<T> {
     // them on the UDP socket, until quiche reports that there are no more
     // packets to be sent.
     pub fn send(&mut self) -> anyhow::Result<()> {
-        let mut pkt = [0; MAX_DATAGRAM_SIZE];
-
         for conn in self.conns.values_mut() {
-            loop {
-                let (size, info) = match conn.quiche.send(&mut pkt) {
-                    Ok(v) => v,
-                    Err(quiche::Error::Done) => return Ok(()),
-                    Err(e) => return Err(e.into()),
-                };
+            let conn = &mut conn.quiche;
 
-                let pkt = &pkt[..size];
-
-                match self.socket.send_to(pkt, info.to) {
-                    Err(err) if err.kind() == io::ErrorKind::WouldBlock => break,
-                    Err(err) => return Err(err.into()),
-                    Ok(_) => (),
-                }
+            if let Err(e) = send_conn(&self.socket, conn) {
+                log::error!("{} send failed: {:?}", conn.trace_id(), e);
+                conn.close(false, 0x1, b"fail").ok();
             }
         }
 
@@ -300,6 +295,27 @@ impl<T: app::App> Server<T> {
     }
 }
 
+// Send any pending packets for the connection over the socket.
+fn send_conn(socket: &mio::net::UdpSocket, conn: &mut quiche::Connection) -> anyhow::Result<()> {
+    let mut pkt = [0; MAX_DATAGRAM_SIZE];
+
+    loop {
+        let (size, info) = match conn.send(&mut pkt) {
+            Ok(v) => v,
+            Err(quiche::Error::Done) => return Ok(()),
+            Err(e) => return Err(e.into()),
+        };
+
+        let pkt = &pkt[..size];
+
+        match socket.send_to(pkt, info.to) {
+            Err(e) if e.kind() == io::ErrorKind::WouldBlock => return Ok(()),
+            Err(e) => return Err(e.into()),
+            Ok(_) => (),
+        }
+    }
+}
+
 /// Generate a stateless retry token.
 ///
 /// The token includes the static string `"quiche"` followed by the IP address