5 ms·

Basically, the server assumes that if the client has ACK'd the message, it can continue sending data. The client assumes that the server has received their ACK

• celticninja 7y ago
  You are just back to the same problem, you need to trust a server. The server is the valley between the generals, you can't be sure what happens there. Do they get the message, or do they het an altered message, both of which will send blue ticks to indicate it has been read.
  • zzbzq 7y ago
    The server is also a general on a mountain
• peheje 7y ago
  I am talking about the Two General's problem which I thought original commentator was referring to as the original problem. In this situation you are describing a server that wants to send a client a message, and both parties need to be sure that they are in agreement when to attack a common enemy they can't deal with alone because the message contains the attack plans and timestamp for attacks. Wikipedia has a good explanation: "The first general may start by sending a message "Attack at 0900 on August 4." However, once dispatched, the first general has no idea whether or not the messenger got through. This uncertainty may lead the first general to hesitate to attack due to the risk of being the sole attacker. To be sure, the second general may send a confirmation back to the first: "I received your message and will attack at 0900 on August 4." However, the messenger carrying the confirmation could face capture and the second general may hesitate, knowing that the first might hold back without the confirmation. Further confirmations may seem like a solution—let the first general send a second confirmation: "I received your confirmation of the planned attack at 0900 on August 4." However, this new messenger from the first general is liable to be captured, too. Thus it quickly becomes evident that no matter how many rounds of confirmation are made, there is no way to guarantee the second requirement that each general be sure the other has agreed to the attack plan. Both generals will always be left wondering whether their last messenger got through. " There is no solution, only a decreasingly smaller change of disagreement e.g. by sending many messages or keep acking each other x amount of rounds (there are other strategies). No timeouts, only death.
  • zaarn 7y ago
    The obvious solution is to bring a ham radio.
  • belinder 7y ago
    What if they send a message that general 1 is going to fire a flare at 0900 and if general 2 fires one too then they both attack. Basically make the confirmation something that you can get without relying on the same method of communication
    • pfarrell 7y ago
      A single line of communication is a constraint of the problem. And anyway, how does general 2 confirm the answer flare was seen?
      • pstuart 7y ago
        With a reciprocal flare :-)