问题

以太坊底层采用了P2P去中心化网络，在不知道任何其它节点的情况之下，它是如何寻找到其它节点并与之通信的呢？

答案

本身一定事先知道了其它节点的

首先厘清两个概念

bootnode

从名字上看得出来，该node作用于 本机节点 boot，预定义在源代码中

staticnode

从名字上看的出来，该node是static的，是 本机节点 稍后的指定连接节点。

cmd/swarm/bootnodes.go中，预定义了很多初始化节点。

// In cmd/swarm/bootnodes.go

var SwarmBootnodes = []string{

// Foundation Swarm Gateway Cluster

"enode://e5c6f9215c919a5450a7b8c14c22535607b69f2c8e1e7f6f430cb25d7a2c27cd1df4c4f18ad7c1d7e5162e271ffcd3f20b1a1467fb6e790e7d727f3b2193de97@52.232.7.187:30399",

"enode://9b2fe07e69ccc7db5fef15793dab7d7d2e697ed92132d6e9548218e68a34613a8671ad03a6658d862b468ed693cae8a0f8f8d37274e4a657ffb59ca84676e45b@52.232.7.187:30400",

"enode://76c1059162c93ef9df0f01097c824d17c492634df211ef4c806935b349082233b63b90c23970254b3b7138d630400f7cf9b71e80355a446a8b733296cb04169a@52.232.7.187:30401",

"enode://ce46bbe2a8263145d65252d52da06e000ad350ed09c876a71ea9544efa42f63c1e1b6cc56307373aaad8f9dd069c90d0ed2dd1530106200e16f4ca681dd8ae2d@52.232.7.187:30402",

"enode://f431e0d6008a6c35c6e670373d828390c8323e53da8158e7bfc43cf07e632cc9e472188be8df01decadea2d4a068f1428caba769b632554a8fb0607bc296988f@52.232.7.187:30403",

"enode://174720abfff83d7392f121108ae50ea54e04889afe020df883655c0f6cb95414db945a0228d8982fe000d86fc9f4b7669161adc89cd7cd56f78f01489ab2b99b@52.232.7.187:30404",

"enode://2ae89be4be61a689b6f9ecee4360a59e185e010ab750f14b63b4ae43d4180e872e18e3437d4386ce44875dc7cc6eb761acba06412fe3178f3dac1dab3b65703e@52.232.7.187:30405",

"enode://24abebe1c0e6d75d6052ce3219a87be8573fd6397b4cb51f0773b83abba9b3d872bfb273cdc07389715b87adfac02f5235f5241442c5089802cbd8d42e310fce@52.232.7.187:30406",

"enode://d08dfa46bfbbdbcaafbb6e34abee4786610f6c91e0b76d7881f0334ac10dda41d8c1f2b6eedffb4493293c335c0ad46776443b2208d1fbbb9e1a90b25ee4eef2@52.232.7.187:30407",

"enode://8d95eb0f837d27581a43668ed3b8783d69dc4e84aa3edd7a0897e026155c8f59c8702fdc0375ee7bac15757c9c78e1315d9b73e4ce59c936db52ea4ae2f501c7@52.232.7.187:30408",

"enode://a5967cc804aebd422baaaba9f06f27c9e695ccab335b61088130f8cbe64e3cdf78793868c7051dfc06eecfe844fad54bc7f6dfaed9db3c7ecef279cb829c25fb@52.232.7.187:30409",

"enode://5f00134d81a8f2ebcc46f8766f627f492893eda48138f811b7de2168308171968f01710bca6da05764e74f14bae41652f554e6321f1aed85fa3461e89d075dbf@52.232.7.187:30410",

"enode://b2142b79b01a5aa66a5e23cc35e78219a8e97bc2412a6698cee24ae02e87078b725d71730711bd62e25ff1aa8658c6633778af8ac14c63814a337c3dd0ebda9f@52.232.7.187:30411",

"enode://1ffa7651094867d6486ce3ef46d27a052c2cb968b618346c6df7040322c7efc3337547ba85d4cbba32e8b31c42c867202554735c06d4c664b9afada2ed0c4b3c@52.232.7.187:30412",

"enode://129e0c3d5f5df12273754f6f703d2424409fa4baa599e0b758c55600169313887855e75b082028d2302ec034b303898cd697cc7ae8256ba924ce927510da2c8d@52.232.7.187:30413",

"enode://419e2dc0d2f5b022cf16b0e28842658284909fa027a0fbbb5e2b755e7f846ea02a8f0b66a7534981edf6a7bcf8a14855344c6668e2cd4476ccd35a11537c9144@52.232.7.187:30414",

"enode://23d55ad900583231b91f2f62e3f72eb498b342afd58b682be3af052eed62b5651094471065981de33d8786f075f05e3cca499503b0ac8ae84b2a06e99f5b0723@52.232.7.187:30415",

"enode://bc56e4158c00e9f616d7ea533def20a89bef959df4e62a768ff238ff4e1e9223f57ecff969941c20921bad98749baae311c0fbebce53bf7bbb9d3dc903640990@52.232.7.187:30416",

"enode://433ce15199c409875e7e72fffd69fdafe746f17b20f0d5555281722a65fde6c80328fab600d37d8624509adc072c445ce0dad4a1c01cff6acf3132c11d429d4d@52.232.7.187:30417",

"enode://632ee95b8f0eac51ef89ceb29313fef3a60050181d66a6b125583b1a225a7694b252edc016efb58aa3b251da756cb73280842a022c658ed405223b2f58626343@52.232.7.187:30418",

"enode://4a0f9bcff7a4b9ee453fb298d0fb222592efe121512e30cd72fef631beb8c6a15153a1456eb073ee18551c0e003c569651a101892dc4124e90b933733a498bb5@52.232.7.187:30419",

"enode://f0d80fbc72d16df30e19aac3051eb56a7aff0c8367686702e01ea132d8b0b3ee00cadd6a859d2cca98ec68d3d574f8a8a87dba2347ec1e2818dc84bc3fa34fae@52.232.7.187:30420",

"enode://a199146906e4f9f2b94b195a8308d9a59a3564b92efaab898a4243fe4c2ad918b7a8e4853d9d901d94fad878270a2669d644591299c3d43de1b298c00b92b4a7@52.232.7.187:30421",

"enode://052036ea8736b37adbfb684d90ce43e11b3591b51f31489d7c726b03618dea4f73b1e659deb928e6bf40564edcdcf08351643f42db3d4ca1c2b5db95dad59e94@52.232.7.187:30422",

"enode://460e2b8c6da8f12fac96c836e7d108f4b7ec55a1c64631bb8992339e117e1c28328fee83af863196e20af1487a655d13e5ceba90e980e92502d5bac5834c1f71@52.232.7.187:30423",

"enode://6d2cdd13741b2e72e9031e1b93c6d9a4e68de2844aa4e939f6a8a8498a7c1d7e2ee4c64217e92a6df08c9a32c6764d173552810ef1bd2ecb356532d389dd2136@52.232.7.187:30424",

"enode://62105fc25ce2cd5b299647f47eaa9211502dc76f0e9f461df915782df7242ac3223e3db04356ae6ed2977ccac20f0b16864406e9ca514a40a004cb6a5d0402aa@52.232.7.187:30425",

"enode://e0e388fc520fd493c33f0ce16685e6f98fb6aec28f2edc14ee6b179594ee519a896425b0025bb6f0e182dd3e468443f19c70885fbc66560d000093a668a86aa8@52.232.7.187:30426",

"enode://63f3353a72521ea10022127a4fe6b4acbef197c3fe668fd9f4805542d8a6fcf79f6335fbab62d180a35e19b739483e740858b113fdd7c13a26ad7b4e318a5aef@52.232.7.187:30427",

"enode://33a42b927085678d4aefd4e70b861cfca6ef5f6c143696c4f755973fd29e64c9e658cad57a66a687a7a156da1e3688b1fbdd17bececff2ee009fff038fa5666b@52.232.7.187:30428",

"enode://259ab5ab5c1daee3eab7e3819ab3177b82d25c29e6c2444fdd3f956e356afae79a72840ccf2d0665fe82c81ebc3b3734da1178ac9fd5d62c67e674b69f86b6be@52.232.7.187:30429",

"enode://558bccad7445ce3fd8db116ed6ab4aed1324fdbdac2348417340c1764dc46d46bffe0728e5b7d5c36f12e794c289f18f57f08f085d2c65c9910a5c7a65b6a66a@52.232.7.187:30430",

"enode://abe60937a0657ffded718e3f84a32987286983be257bdd6004775c4b525747c2b598f4fac49c8de324de5ce75b22673fa541a7ce2d555fb7f8ca325744ae3577@52.232.7.187:30431",

"enode://bce6f0aaa5b230742680084df71d4f026b3eff7f564265599216a1b06b765303fdc9325de30ffd5dfdaf302ce4b14322891d2faea50ce2ca298d7409f5858339@52.232.7.187:30432",

"enode://21b957c4e03277d42be6660730ec1b93f540764f26c6abdb54d006611139c7081248486206dfbf64fcaffd62589e9c6b8ea77a5297e4b21a605f1bcf49483ed0@52.232.7.187:30433",

"enode://ff104e30e64f24c3d7328acee8b13354e5551bc8d60bb25ecbd9632d955c7e34bb2d969482d173355baad91c8282f8b592624eb3929151090da3b4448d4d58fb@52.232.7.187:30434",

"enode://c76e2b5f81a521bceaec1518926a21380a345df9cf463461562c6845795512497fb67679e155fc96a74350f8b78de8f4c135dd52b106dbbb9795452021d09ea5@52.232.7.187:30435",

"enode://3288fd860105164f3e9b69934c4eb18f7146cfab31b5a671f994e21a36e9287766e5f9f075aefbc404538c77f7c2eb2a4495020a7633a1c3970d94e9fa770aeb@52.232.7.187:30436",

"enode://6cea859c7396d46b20cfcaa80f9a11cd112f8684f2f782f7b4c0e1e0af9212113429522075101923b9b957603e6c32095a6a07b5e5e35183c521952ee108dfaf@52.232.7.187:30437",

"enode://f628ec56e4ca8317cc24cc4ac9b27b95edcce7b96e1c7f3b53e30de4a8580fe44f2f0694a513bdb0a431acaf2824074d6ace4690247bbc34c14f426af8c056ea@52.232.7.187:30438",

"enode://055ec8b26fc105c4f97970a1cce9773a5e34c03f511b839db742198a1c571e292c54aa799e9afb991cc8a560529b8cdf3e0c344bc6c282aff2f68eec59361ddf@52.232.7.187:30439",

"enode://48cb0d430c328974226aa33a931d8446cd5a8d40f3ead8f4ce7ad60faa1278192eb6d58bed91258d63e81f255fc107eec2425ce2ae8b22350dd556076e160610@52.232.7.187:30440",

"enode://3fadb7af7f770d5ffc6b073b8d42834bebb18ce1fe8a4fe270d2b799e7051327093960dc61d9a18870db288f7746a0e6ea2a013cd6ab0e5f97ca08199473aace@52.232.7.187:30441",

"enode://a5d7168024c9992769cf380ffa559a64b4f39a29d468f579559863814eb0ae0ed689ac0871a3a2b4c78b03297485ec322d578281131ef5d5c09a4beb6200a97a@52.232.7.187:30442",

"enode://9c57744c5b2c2d71abcbe80512652f9234d4ab041b768a2a886ab390fe6f184860f40e113290698652d7e20a8ac74d27ac8671db23eb475b6c5e6253e4693bf8@52.232.7.187:30443",

"enode://daca9ff0c3176045a0e0ed228dee00ec86bc0939b135dc6b1caa23745d20fd0332e1ee74ad04020e89df56c7146d831a91b89d15ca3df05ba7618769fefab376@52.232.7.187:30444",

"enode://a3f6af59428cb4b9acb198db15ef5554fa43c2b0c18e468a269722d64a27218963a2975eaf82750b6262e42192b5e3669ea51337b4cda62b33987981bc5e0c1a@52.232.7.187:30445",

"enode://fe571422fa4651c3354c85dac61911a6a6520dd3c0332967a49d4133ca30e16a8a4946fa73ca2cb5de77917ea701a905e1c3015b2f4defcd53132b61cc84127a@52.232.7.187:30446",

// Mainframe

"enode://ee9a5a571ea6c8a59f9a8bb2c569c865e922b41c91d09b942e8c1d4dd2e1725bd2c26149da14de1f6321a2c6fdf1e07c503c3e093fb61696daebf74d6acd916b@54.186.219.160:30399",

"enode://a03f0562ecb8a992ad5242345535e73483cdc18ab934d36bf24b567d43447c2cea68f89f1d51d504dd13acc30f24ebce5a150bea2ccb1b722122ce4271dc199d@52.67.248.147:30399",

"enode://e2cbf9eafd85903d3b1c56743035284320695e0072bc8d7396e0542aa5e1c321b236f67eab66b79c2f15d4447fa4bbe74dd67d0467da23e7eb829f60ec8a812b@13.58.169.1:30399",

"enode://8b8c6bda6047f1cad9fab2db4d3d02b7aa26279902c32879f7bcd4a7d189fee77fdc36ee151ce6b84279b4792e72578fd529d2274d014132465758fbfee51cee@13.209.13.15:30399",

"enode://63f6a8818927e429585287cf2ca0cb9b11fa990b7b9b331c2962cdc6f21807a2473b26e8256225c26caff70d7218e59586d704d49061452c6852e382c885d03c@35.154.106.174:30399",

"enode://ed4bd3b794ed73f18e6dcc70c6624dfec63b5654f6ab54e8f40b16eff8afbd342d4230e099ddea40e84423f81b2d2ea79799dc345257b1fec6f6c422c9d008f7@52.213.20.99:30399",

}

配置生效的地方

// In /cmd/swarm/main.go

func setSwarmBootstrapNodes(ctx *cli.Context, cfg *node.Config) {

if ctx.GlobalIsSet(utils.BootnodesFlag.Name) || ctx.GlobalIsSet(utils.BootnodesV4Flag.Name) {

return

}

cfg.P2P.BootstrapNodes = []*discover.Node{}

for _, url := range SwarmBootnodes {

node, err := discover.ParseNode(url)

if err != nil {

log.Error("Bootstrap URL invalid", "enode", url, "err", err)

}

cfg.P2P.BootstrapNodes = append(cfg.P2P.BootstrapNodes, node)

}

log.Debug("added default swarm bootnodes", "length", len(cfg.P2P.BootstrapNodes))

}