Implemented sequence tracking.

src/common/sequence.nim

@@ -0,0 +1,28 @@
+import tables 
+import ./[types, utils]
+
+var sequenceTable {.global.}: Table[uint32, uint64]
+
+proc nextSequence*(agentId: uint32): uint64 = 
+    sequenceTable[agentId] = sequenceTable.getOrDefault(agentId, 0'u64) + 1
+    return sequenceTable[agentId]
+
+proc validateSequence*(agentId: uint32, seqNr: uint64, packetType: uint8): bool = 
+    let lastSeqNr = sequenceTable.getOrDefault(agentId, 0'u64)
+
+    # Heartbeat messages are not used for sequence tracking
+    if cast[PacketType](packetType) == MSG_HEARTBEAT: 
+        return true
+
+    # In order to keep agents running after server restart, accept all connection with seqNr = 1, to update the table
+    if seqNr == 1'u64:
+        sequenceTable[agentId] = seqNr
+        return true
+
+    # Validate that the sequence number of the current packet is higher than the currently stored one 
+    if seqNr <= lastSeqNr: 
+        return false 
+
+    # Update sequence number
+    sequenceTable[agentId] = seqNr
+    return true

src/common/types.nim

@@ -74,7 +74,6 @@ type
 
     Task* = object 
         header*: Header
-
         taskId*: uint32         # [4 bytes ] task id
         listenerId*: uint32     # [4 bytes ] listener id
         timestamp*: uint32      # [4 bytes ] unix timestamp
@@ -84,7 +83,6 @@ type
 
     TaskResult* = object 
         header*: Header 
-
         taskId*: uint32         # [4 bytes ] task id
         listenerId*: uint32     # [4 bytes ] listener id
         timestamp*: uint32      # [4 bytes ] unix timestamp
@@ -103,6 +101,7 @@ type
 
 # Registration binary structure 
 type 
+
     # All variable length fields are stored as seq[byte], prefixed with 4 bytes indicating the length of the following data
     AgentMetadata* = object 
         listenerId*: uint32
@@ -151,7 +150,7 @@ type
         port*: int
         protocol*: Protocol
 
-# Server structure
+# Server context structure
 type 
     KeyPair* = object 
         privateKey*: Key 
@@ -165,7 +164,7 @@ type
         interactAgent*: Agent
         keyPair*: KeyPair
 
-# Agent Config
+# Agent config
 type
     AgentConfig* = ref object
         agentId*: string