1. I am A
I have heard: no one A B
Have heard list
Have heard list

2. I am A
I have heard: no one A B
Have heard list
Have heard list A

3. I am B
I have heard: A A B
Have heard list
Have heard list A

4. A B A I am B I have heard: A Have heard list Have heard list
B and B hears me A

5. A B A I am A I have heard: B Have heard list Have heard list
B and B hears me A

6. A B I am A I have heard: B, C, D Have heard list Have heard list
B and B hears me
A and A hears me

7. List unidirectionalNeighbors bidirectionalNeighbors
A neighbor can be in at most one list
(we could allow a neighbor to be in both, but let’s not do it that way)

8. A B What is in the hello message? - The source of the message I am A
I have heard: no one A B
Have heard list
Have heard list
Unidirectional Neighbors
Bidirectional Neighbors
Unidirectional Neighbors
Bidirectional Neighbors

9. A B A A What is in the hello message? The source of the message I am A
I have heard: no one A B
Have heard list
Have heard list A
Unidirectional Neighbors
Bidirectional Neighbors
Unidirectional Neighbors
Bidirectional Neighbors A

10. A B A A What is in the hello message? The source of the message
Any element in the unidirectional neighbors list
I am B
I have heard: A A B
Have heard list
Have heard list A
Unidirectional Neighbors
Bidirectional Neighbors
Unidirectional Neighbors
Bidirectional Neighbors A

11. A B A B A What is in the hello message? The source of the message
Any element in the unidirectional neighbors list
I am B
I have heard: A A B
Have heard list
Have heard list
B and B hears me A
Unidirectional Neighbors
Bidirectional Neighbors
Unidirectional Neighbors
Bidirectional Neighbors B A

12. A B A B A What is in the hello message? The source of the message
Any element in the unidirectional neighbors list
Any element in the bidirectional neighbors list
I am A
I have heard: B A B
Have heard list
Have heard list
B and B hears me A
Unidirectional Neighbors
Bidirectional Neighbors
Unidirectional Neighbors
Bidirectional Neighbors B A

13. A B A B A What is in the hello message? The source of the message
Any element in the unidirectional neighbors list
Any element in the bidirectional neighbors list
HelloMessage helloMessage;
helloMessage.source = thisHost;
for (NeighborInfo &neighbor : bidirectionalNeighbors) {
helloMessage. addToNeighborsList(neighbor); }
for (NeighborInfo &neighbor : unidirectionalNeighbors)
I am A
I have heard: B A B
Have heard list
Have heard list
B and B hears me A
Unidirectional Neighbors
Bidirectional Neighbors
Unidirectional Neighbors
Bidirectional Neighbors B A

14. Sending a hello message
HelloMessage helloMessage;
// fill in hello message
Packet pkt;
pkt.getPacketReadyForWriting();
helloMessage.addToPacket(pkt);
udpSocket.sendTo(pkt, destination);
What should the destination be?
Send the hello message to every neighbor
HelloMessage helloMessage;
// TODO: fill hello message
// make pkt
for (NeighborInfo &neighbor : bidirectionalNeighbors) {
udpSocket.sendTo(pkt, neighbor); }
for (NeighborInfo &neighbor : unidirectionalNeighbors)
Pick a new neighbor at random, and send a hello to them
What if you have no neighbors?
What if you don’t have enough neighbors?
NeighborInfo temp = selectNeighbor(bidirectionalNeighbors,
unidirectionalNeighbors, allHosts, thisHost);
udpSocket.sendTo(pkt, temp);

15. Sending a hello message
HelloMessage helloMessage;
// fill in hello message
Packet pkt;
pkt.getPacketReadyForWriting();
helloMessage.addToPacket(pkt);
udpSocket.sendTo(pkt, destination);
What should the destination be?
Send the hello message to every neighbor
HelloMessage helloMessage;
// TODO: fill hello message
// make pkt
for (NeighborInfo &neighbor : bidirectionalNeighbors) {
udpSocket.sendTo(pkt, neighbor); }
for (NeighborInfo &neighbor : unidirectionalNeighbors)
Pick a new neighbor at random, and send a hello to them
What if you have no neighbors?
What if you don’t have enough neighbors?
If (bidirectionalNeighbors.size() + unidirectionalNeighbors.size()
< TARGET_NUMBER_OF_NEIGHBORS) {
NeighborInfo temp = selectNeighbor(bidirectionalNeighbors,
unidirectionalNeighbors, allHosts, thisHost);
udpSocket.sendTo(pkt, temp); }