Connecting to the network

Connecting to the network

How Peers Are Found

Geth continuously attempts to connect to other nodes on the network until it has peers. If you have UPnP enabled on your router or run ethereum on an Internet-facing server, it will also accept connections from other nodes.

Geth finds peers through something called the discovery protocol. In the discovery protocol, nodes are gossipping with each other to find out about other nodes on the network. In order to get going initially, geth uses a set of bootstrap nodes whose endpoints are recorded in the source code.

To change the bootnodes on startup, use the --bootnodes option and separate the nodes by spaces. For example:

geth --bootnodes "enode://pubkey1@ip1:port1 enode://pubkey2@ip2:port2 enode://pubkey3@ip3:port3"

Common Problems With Connectivity

Sometimes you just can't get connected. The most common reasons are as follows:

• Your local time might be incorrect. An accurate clock is required to participate in the Ethereum network.
• Some firewall configurations can prevent UDP traffic from flowing. You can use the static nodes feature or admin.addPeer() on the console to configure connections by hand.

Checking Connectivity

To check how many peers the client is connected to in the interactive console, check the net object:

> net
{
  listening: true,
  peerCount: 4
}

To get more information about the connected peers, such as IP address and port number, supported protocols, use the peers() function of the admin object:

> admin.peers()
[{
  ID: 'a4de274d3a159e10c2c9a68c326511236381b84c9ec52e72ad732eb0b2b1a2277938f78593cdbe734e6002bf23114d434a085d260514ab336d4acdc312db671b',
  Name: 'Geth/v0.9.14/linux/go1.4.2',
  Caps: 'eth/60',
  RemoteAddress: '5.9.150.40:30301',
  LocalAddress: '192.168.0.28:39219'
}, {
  ID: 'a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c',
  Name: 'Geth/v0.9.15/linux/go1.4.2',
  Caps: 'eth/60',
  RemoteAddress: '52.16.188.185:30303',
  LocalAddress: '192.168.0.28:50995'
}, {
  ID: 'f6ba1f1d9241d48138136ccf5baa6c2c8b008435a1c2bd009ca52fb8edbbc991eba36376beaee9d45f16d5dcbf2ed0bc23006c505d57ffcf70921bd94aa7a172',
  Name: 'pyethapp_dd52/v0.9.13/linux2/py2.7.9',
  Caps: 'eth/60, p2p/3',
  RemoteAddress: '144.76.62.101:30303',
  LocalAddress: '192.168.0.28:40454'
}, {
  ID: 'f4642fa65af50cfdea8fa7414a5def7bb7991478b768e296f5e4a54e8b995de102e0ceae2e826f293c481b5325f89be6d207b003382e18a8ecba66fbaf6416c0',
  Name: '++eth/Zeppelin/Rascal/v0.9.14/Release/Darwin/clang/int',
  Caps: 'eth/60, shh/2',
  RemoteAddress: '129.16.191.64:30303',
  LocalAddress: '192.168.0.28:39705'
} ]

To check the ports used by geth and also find your enode URI run:

> admin.nodeInfo()
{
  Name: 'Geth/v0.9.14/darwin/go1.4.2',
  NodeUrl: 'enode://3414c01c19aa75a34f2dbd2f8d0898dc79d6b219ad77f8155abf1a287ce2ba60f14998a3a98c0cf14915eabfdacf914a92b27a01769de18fa2d049dbf4c17694@[::]:30303',
  NodeID: '3414c01c19aa75a34f2dbd2f8d0898dc79d6b219ad77f8155abf1a287ce2ba60f14998a3a98c0cf14915eabfdacf914a92b27a01769de18fa2d049dbf4c17694',
  IP: '::',
  DiscPort: 30303,
  TCPPort: 30303,
  Td: '2044952618444',
  ListenAddr: '[::]:30303'
}

Custom Networks

Sometimes you might not need to connect to the live public network, you can instead choose to create your own private testnet. This is very useful if you don't need to test external contracts and want just to test the technology, because you won't have to compete with other miners and will easily generate a lot of test ether to play around (replace 12345 with any non-negative number):

geth -—networkid="12345" console

Static nodes

Geth also supports a feature called static nodes if you have certain peers you always want to connect to. Static nodes are re-connected on disconnects. You can configure permanent static nodes by putting something like the following into <datadir>/static-nodes.json:

[
	"enode://f4642fa65af50cfdea8fa7414a5def7bb7991478b768e296f5e4a54e8b995de102e0ceae2e826f293c481b5325f89be6d207b003382e18a8ecba66fbaf6416c0@33.4.2.1:30303",

"enode://pubkey@ip:port" ]