Security

Peer-to-peer template

A simple template for a project with a peer-to-peer architecture. In the system, each node is able to send a ping to all other nodes in the system, and in return get a response from each node, telling how many times it has pinged that specific node. As each node always sends a ping to all nodes at the same time, the response will always be the same from all nodes.

How to run

This distributed system has a hardcoded amount of nodes = 3. To run the system, you must run three separate processes with the commands:

go run . 0

go run . 1

go run . 2

go run . 3

Notes about the main.go file

Each node has to act as server and client at the same time. In the main() function, we both setup the node as a server, listening to its own port (lines 30-42), and also set it up as a client, connecting to the other peers as servers (lines 44-60). Both of these are necessary for the whole architecture to work.

Changing the ports

In this example, our three nodes run on ports 5000, 5001 and 5002 - this is decided on lines 17-18 and in the "How to run" section. Changing the arguments in the commands, i.e. from go run . 0 to go run . 20, will change the port from 5000 to 5020. Changing the last part of line 18 from 5000 to 3000 will change the port in the same way.

Changing the ports will affect the "find the other peers" part of the main() function. If you make changes to which port each node runs on, make sure to change line 45 so that it matches your new ports.

Changing the amount of nodes

Line 44 starts a for loop which runs three times, since there are three nodes in the system. Increasing the number to e.g. 5 will enable you to have 5 nodes in the system, and you would simply need to start two more processes with

go run . 3

go run . 4

Changing the functionality

You will need a function for each rpc - such that the "server-side" of the node knows what to do, when another node tries to communicate with it. In this example, the Ping(...) function is the rpc function.

You do not necessarily need a function for the "client-side" of the node, but there is some clean-code-good-practice in doing it as such. It is up to you though! In this example, we have a sendPingToAll() function, where the peer acts as a client, sends a ping to all the peers, it has connected to, and then prints the replies it gets.

The main functionality is in lines 62-65. This is where we decide what the peer should do. In this example, the peer waits for a newline character to be entered and then calls the sendPingToAll() function. This can be changed, such that it calls it every 10 seconds, or such that it does something completely different.