ProtocolManager 의 분석

//eth/handler.go
type ProtocolManager struct {
    networkId uint64

    fastSync  uint32 // Flag whether fast sync is enabled (gets disabled if we already have blocks)
    acceptTxs uint32 // Flag whether we're considered synchronised (enables transaction processing)

    txpool      txPool
    blockchain  *core.BlockChain
    chainconfig *params.ChainConfig
    maxPeers    int

    downloader *downloader.Downloader
    fetcher    *fetcher.Fetcher
    peers      *peerSet

    SubProtocols []p2p.Protocol

    eventMux      *event.TypeMux
    txCh          chan core.TxPreEvent
    txSub         event.Subscription
    minedBlockSub *event.TypeMuxSubscription

    // channels for fetcher, syncer, txsyncLoop
    newPeerCh   chan *peer
    txsyncCh    chan *txsync
    quitSync    chan struct{}
    noMorePeers chan struct{}

    // wait group is used for graceful shutdowns during downloading
    // and processing
    wg sync.WaitGroup
}

//eth/handler.go
manager.SubProtocols = append(manager.SubProtocols, p2p.Protocol{
            Name:    ProtocolName,
            Version: version,
            Length:  ProtocolLengths[i],
            Run: func(p *p2p.Peer, rw p2p.MsgReadWriter) error {
                peer := manager.newPeer(int(version), p, rw)
                select {
                case manager.newPeerCh