diff --git a/src/runtime2/communication.rs b/src/runtime2/communication.rs
index cebb7b67d319eb1fb2106c9ac06857d5a575659f..335f4c6d0864416a0135f0c9522eb433f19f3328 100644
--- a/src/runtime2/communication.rs
+++ b/src/runtime2/communication.rs
@@ -17,29 +17,6 @@ impl PortId {
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy)]
-pub enum PortKind {
-    Putter,
-    Getter,
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum PortState {
-    Open,
-    BlockedDueToPeerChange,
-    BlockedDueToFullBuffers,
-    Closed,
-}
-
-impl PortState {
-    pub fn is_blocked(&self) -> bool {
-        match self {
-            PortState::BlockedDueToPeerChange | PortState::BlockedDueToFullBuffers => true,
-            PortState::Open | PortState::Closed => false,
-        }
-    }
-}
-
 pub struct Channel {
     pub putter_id: PortId,
     pub getter_id: PortId,
@@ -111,6 +88,7 @@ pub struct SyncSolutionGetterPort {
     pub peer_comp_id: CompId,
     pub peer_port_id: PortId,
     pub mapping: u32,
+    pub failed: bool,
 }
 
 /// Putter port in a solution. A putter may not be certain about who its peer
@@ -120,6 +98,7 @@ pub struct SyncSolutionPutterPort {
     pub self_comp_id: CompId,
     pub self_port_id: PortId,
     pub mapping: u32,
+    pub failed: bool,
 }
 
 #[derive(Debug)]
@@ -171,14 +150,21 @@ pub struct ControlMessage {
     pub content: ControlMessageContent,
 }
 
+/// Content of a control message. If the content refers to a port then the
+/// `target_port_id` field is the one that it refers to.
 #[derive(Copy, Clone, Debug)]
 pub enum ControlMessageContent {
     Ack,
-    BlockPort(PortId),
-    UnblockPort(PortId),
-    ClosePort(PortId),
-    PortPeerChangedBlock(PortId),
-    PortPeerChangedUnblock(PortId, CompId),
+    BlockPort,
+    UnblockPort,
+    ClosePort(ControlMessageClosePort),
+    PortPeerChangedBlock,
+    PortPeerChangedUnblock(PortId, CompId), // contains (new_port_id, new_component_id)
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct ControlMessageClosePort {
+    pub closed_in_sync_round: bool, // needed to ensure correct handling of errors
 }
 
 // -----------------------------------------------------------------------------