diff --git a/src/runtime/mod.rs b/src/runtime/mod.rs
index 592040558a0a2487e01a595f95fc52ce4fc4c610..6ae66019b5754d73bf9fd9c1e5d992d8304c83c4 100644
--- a/src/runtime/mod.rs
+++ b/src/runtime/mod.rs
@@ -123,6 +123,10 @@ struct CommMsg {
 #[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
 enum CommMsgContents {
     SendPayload(SendPayloadMsg),
+    CommCtrl(CommCtrlMsg),
+}
+#[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
+enum CommCtrlMsg {
     Suggest { suggestion: Decision }, // SINKWARD
     Announce { decision: Decision },  // SINKAWAYS
 }
@@ -176,6 +180,10 @@ struct IdManager {
     proto_component_suffix_stream: U32Stream,
 }
 #[derive(Debug)]
+struct UdpInBuffer {
+    byte_vec: Vec<u8>,
+}
+#[derive(Debug)]
 struct SpecVarStream {
     connector_id: ConnectorId,
     port_suffix_stream: U32Stream,
@@ -187,16 +195,24 @@ struct EndpointManager {
     // 2. Events is empty
     poll: Poll,
     events: Events,
-    polled_undrained: VecSet<usize>,
     delayed_messages: Vec<(usize, Msg)>,
     undelayed_messages: Vec<(usize, Msg)>,
-    net_endpoint_exts: Vec<NetEndpointExt>,
+    net_endpoint_store: EndpointStore<NetEndpointExt>,
+    udp_endpoint_store: EndpointStore<UdpEndpointExt>,
+    udp_in_buffer: UdpInBuffer,
+}
+#[derive(Debug)]
+struct EndpointStore<T> {
+    endpoint_exts: Vec<T>,
+    polled_undrained: VecSet<usize>,
 }
+#[derive(Debug)]
 struct UdpEndpointExt {
-    sock: UdpSocket,
+    sock: UdpSocket, // already bound and connected
+    outgoing_payloads: HashMap<Predicate, Payload>,
+    incoming_round_spec_var: Option<SpecVar>,
     getter_for_incoming: PortId,
-    outgoing_buffer: HashMap<Predicate, Payload>,
-    incoming_buffer: Vec<Payload>,
+    incoming_payloads: Vec<Payload>,
 }
 #[derive(Clone, Debug, Default, serde::Serialize, serde::Deserialize)]
 struct PortInfo {
@@ -247,6 +263,15 @@ enum TokenTarget {
     UdpEndpoint { index: usize },
     Waker,
 }
+trait RoundCtxTrait {
+    fn get_deadline(&self) -> &Option<Instant>;
+    fn getter_add(&mut self, getter: PortId, msg: SendPayloadMsg);
+}
+enum CommRecvOk {
+    TimeoutWithoutNew,
+    NewPayloadMsgs,
+    NewControlMsg { net_endpoint_index: usize, msg: CommCtrlMsg },
+}
 ////////////////
 fn would_block(err: &std::io::Error) -> bool {
     err.kind() == std::io::ErrorKind::WouldBlock
@@ -258,7 +283,7 @@ impl TokenTarget {
 }
 impl From<Token> for TokenTarget {
     fn from(Token(index): Token) -> Self {
-        if index == Self::MAX_INDEX {
+        if index == Self::WAKER_TOKEN {
             TokenTarget::Waker
         } else if let Some(shifted) = index.checked_sub(Self::HALFWAY_INDEX) {
             TokenTarget::UdpEndpoint { index: shifted }
@@ -270,7 +295,7 @@ impl From<Token> for TokenTarget {
 impl Into<Token> for TokenTarget {
     fn into(self) -> Token {
         match self {
-            TokenTarget::Waker => Token(Self::MAX_INDEX),
+            TokenTarget::Waker => Token(Self::WAKER_TOKEN),
             TokenTarget::UdpEndpoint { index } => Token(index + Self::HALFWAY_INDEX),
             TokenTarget::NetEndpoint { index } => Token(index),
         }
@@ -426,6 +451,17 @@ impl Predicate {
         self.assigned.insert(k, v);
         self
     }
+
+    pub fn assigns_subset(&self, maybe_superset: &Self) -> bool {
+        for (var, val) in self.assigned.iter() {
+            match maybe_superset.assigned.get(var) {
+                Some(val2) if val2 == val => {}
+                _ => return false,
+            }
+        }
+        true
+    }
+
     // returns true IFF self.unify would return Equivalent OR FormerNotLatter
     pub fn consistent_with(&self, other: &Self) -> bool {
         let [larger, smaller] =
@@ -557,6 +593,10 @@ impl SpecVal {
         self == Self::FIRING
         // all else treated as SILENT
     }
+    fn nth_domain_element(n: usize) -> Self {
+        let n: u16 = n.try_into().unwrap();
+        SpecVal(n)
+    }
     fn iter_domain() -> impl Iterator<Item = Self> {
         (0..).map(SpecVal)
     }
@@ -566,3 +606,19 @@ impl Debug for SpecVal {
         self.0.fmt(f)
     }
 }
+impl Default for UdpInBuffer {
+    fn default() -> Self {
+        let mut byte_vec = Vec::with_capacity(Self::CAPACITY);
+        unsafe {
+            // safe! this vector is guaranteed to have sufficient capacity
+            byte_vec.set_len(Self::CAPACITY);
+        }
+        Self { byte_vec }
+    }
+}
+impl UdpInBuffer {
+    const CAPACITY: usize = u16::MAX as usize;
+    fn as_mut_slice(&mut self) -> &mut [u8] {
+        self.byte_vec.as_mut_slice()
+    }
+}