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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 commas. 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. Check your OS for how to resync your clock (example sudo ntpdate -s time.nist.gov) because even 12 seconds too fast can lead to 0 peers.
- 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.
To start geth without the discovery protocol, you can use the --nodiscover
parameter. You only want this is you are running a test node or an experimental test network with fixed nodes.
Checking Connectivity
To check how many peers the client is connected to in the interactive console, the net
module has two attributes give you info about the number of peers and whether you are a listening node.
> net.listening
true
> net.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()
returns the list of currently connected peers.
> 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
It is also possible to run geth with a custom genesis block from a JSON file
by supplying the --genesis
flag. The genesis JSON file should have the following
format:
{
"alloc": {
"dbdbdb2cbd23b783741e8d7fcf51e459b497e4a6": {
"balance": "1606938044258990275541962092341162602522202993782792835301376"
},
"e6716f9544a56c530d868e4bfbacb172315bdead": {
"balance": "1606938044258990275541962092341162602522202993782792835301376"
},
...
},
"nonce": "0x000000000000002a",
"difficulty": "0x020000",
"mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
"coinbase": "0x0000000000000000000000000000000000000000",
"timestamp": "0x00",
"parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
"extraData": "0x",
"gasLimit": "0x2fefd8"
}
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>/geth/static-nodes.json
:
[
"enode://f4642fa65af50cfdea8fa7414a5def7bb7991478b768e296f5e4a54e8b995de102e0ceae2e826f293c481b5325f89be6d207b003382e18a8ecba66fbaf6416c0@33.4.2.1:30303",
"enode://pubkey@ip:port"
]
You can also add static nodes at runtime via the js console using admin.addPeer()
:
admin.addPeer("enode://f4642fa65af50cfdea8fa7414a5def7bb7991478b768e296f5e4a54e8b995de102e0ceae2e826f293c481b5325f89be6d207b003382e18a8ecba66fbaf6416c0@33.4.2.1:30303")
Caveat: Currently the console is lacking support for removing a peer, increasing peercount or adding a non-static peer but not to keep try reconnecting.