Resolving several connection issues:

- Adding peers to peer pool on incoming connection
- Exclude bootnodes from nodes to connect to
- Check if peer is already connected to before adding to peer pool
- Check if peer is still connected to before removing from peer pool

eth_p2p.nim

@@ -58,10 +58,15 @@ proc processIncoming(server: StreamServer,
   yield peerfut
   if not peerfut.failed:
     let peer = peerfut.read()
-    echo "TODO: Add peer to the pool..."
+    if peer.remote notin node.peerPool.connectedNodes:
+      node.peerPool.connectedNodes[peer.remote] = peer
+      for o in node.peerPool.observers.values:
+        if not o.onPeerConnected.isNil:
+          o.onPeerConnected(peer)
+    else:
+      debug "Disconnecting already connected node"
+      await peer.disconnect(AlreadyConnected)
   else:
-    echo "Could not establish connection with incoming peer ",
-         $remote.remoteAddress()
     remote.close()
 
 proc startListening*(node: EthereumNode) =

eth_p2p/peer_pool.nim

@@ -2,7 +2,7 @@
 # on the given network.
 
 import
-  os, tables, times, random,
+  os, tables, times, random, sequtils,
   asyncdispatch2, chronicles, rlp, eth_keys,
   private/types, discovery, kademlia, rlpx
 
@@ -28,7 +28,7 @@ proc newPeerPool*(network: EthereumNode,
 template ensureFuture(f: untyped) = asyncCheck f
 
 proc nodesToConnect(p: PeerPool): seq[Node] {.inline.} =
-  p.discovery.randomNodes(p.minPeers)
+  p.discovery.randomNodes(p.minPeers).filterIt(it notin p.discovery.bootstrapNodes)
 
 proc addObserver(p: PeerPool, observerId: int, observer: PeerObserver) =
   assert(observerId notin p.observers)
@@ -99,17 +99,22 @@ proc lookupRandomNode(p: PeerPool) {.async.} =
     discard
   p.lastLookupTime = epochTime()
 
-proc getRandomBootnode(p: PeerPool): seq[Node] =
+proc getRandomBootnode(p: PeerPool): Node =
-  @[p.discovery.bootstrapNodes.rand()]
+  p.discovery.bootstrapNodes.rand()
 
 proc connectToNode*(p: PeerPool, n: Node) {.async.} =
   let peer = await p.connect(n)
   if not peer.isNil:
     info "Connection established", peer
-    p.connectedNodes[peer.remote] = peer
+    if peer.remote notin p.connectedNodes:
-    for o in p.observers.values:
+      p.connectedNodes[peer.remote] = peer
-      if not o.onPeerConnected.isNil:
+      for o in p.observers.values:
-        o.onPeerConnected(peer)
+        if not o.onPeerConnected.isNil:
+          o.onPeerConnected(peer)
+    else:
+      # In case an incoming connection was added in the meanwhile
+      debug "Disconnecting peer", reason = AlreadyConnected
+      await peer.disconnect(AlreadyConnected)
 
 proc connectToNodes(p: PeerPool, nodes: seq[Node]) {.async.} =
   for node in nodes:
@@ -149,7 +154,7 @@ proc maybeConnectToMorePeers(p: PeerPool) {.async.} =
   # be full of bad peers, so if we can't connect to any peers we try a random
   # bootstrap node as well.
   if p.connectedNodes.len == 0:
-    await p.connectToNodes(p.getRandomBootnode())
+    await p.connectToNode(p.getRandomBootnode())
 
 proc run(p: PeerPool) {.async.} =
   info "Running PeerPool..."

eth_p2p/rlpx.nim

@@ -1108,7 +1108,7 @@ rlpxProtocol p2p(version = 0):
     discard
 
 proc removePeer(network: EthereumNode, peer: Peer) =
-  if network.peerPool != nil:
+  if network.peerPool != nil and not peer.remote.isNil:
     network.peerPool.connectedNodes.del(peer.remote)
 
     for observer in network.peerPool.observers.values:
@@ -1365,12 +1365,22 @@ proc rlpxAccept*(node: EthereumNode,
     result.remote = newNode(initEnode(handshake.remoteHPubkey, address))
 
     await postHelloSteps(result, response)
+  except PeerDisconnected as e:
+    if e.reason == AlreadyConnected:
+      debug "Disconnect during rlpxAccept", reason = e.reason
+    else:
+      debug "Unexpected disconnect during rlpxAccept", reason = e.reason
+    transport.close()
+    result = nil
+    raise e
   except:
+    let e = getCurrentException()
     error "Exception in rlpxAccept",
           err = getCurrentExceptionMsg(),
           stackTrace = getCurrentException().getStackTrace()
     transport.close()
     result = nil
+    raise e
 
 when isMainModule: