以太坊系列之十九 对p2p模块server的理解

type transport interface {
    // The two handshakes.
    doEncHandshake(prv *ecdsa.PrivateKey, dialDest *discover.Node) (discover.NodeID, error)
    doProtoHandshake(our *protoHandshake) (*protoHandshake, error)
    // The MsgReadWriter can only be used after the encryption
    // handshake has completed. The code uses conn.id to track this
    // by setting it to a non-nil value after the encryption handshake.
    MsgReadWriter
    // transports must provide Close because we use MsgPipe in some of
    // the tests. Closing the actual network connection doesn't do
    // anything in those tests because NsgPipe doesn't use it.
    close(err error)
}
type conn struct {
    fd        net.Conn
    transport //指向真正的transport实现,rlpx
    flags     connFlag
    cont      chan error      // The run loop uses cont to signal errors to setupConn.
    id        discover.NodeID // valid after the encryption handshake
    caps      []Cap           // valid after the protocol handshake
    name      string          // valid after the protocol handshake
}
// Server manages all peer connections.
type Server struct {
    // Config fields may not be modified while the server is running.
    Config

    // Hooks for testing. These are useful because we can inhibit
    // the whole protocol stack.
    newTransport func(net.Conn) transport 
    newPeerHook  func(*Peer)

    lock    sync.Mutex // protects running
    running bool

    ntab         discoverTable
    listener     net.Listener
    ourHandshake *protoHandshake
    lastLookup   time.Time
    DiscV5       *discv5.Network

    // These are for Peers, PeerCount (and nothing else).
    peerOp     chan peerOpFunc
    peerOpDone chan struct{}

    quit          chan struct{}
    addstatic     chan *discover.Node
    removestatic  chan *discover.Node
    posthandshake chan *conn
    addpeer       chan *conn
    delpeer       chan peerDrop
    loopWG        sync.WaitGroup // loop, listenLoop
}

Server是暴露给上层使用的接口,配置完毕以后,直接调用Start就可以了,其中Start做了非常复杂的工作.主要是启动监听端口,等待连接.这里会创建多个goroutine,完毕以后进入run,run实际上就是一个汇聚层,其他的goroutine都回把得到的结果通过channel形式汇报给主goroutine,也就是run,由run集中处理,避免并发冲突.
另外run的另一个重要功能就是不断的调用dialstate,来创建连接,维护与结点的连接.也就是scheduleTasks.

创建Server,对于用户来说主要是指定一个newPeerHook,这样当有了新的结点以后,就可以和这些结点进行通信,通信的格式是Msg,这个应该是用户最关心的.

newTransport 是和结点建立连接(tcp或者udp)以后进行协商密钥,协议握手的地方,实际上是newRLPX.也就是rlpx来负责.

这里先说说Config,这里的PrivateKey必须指定,否则会出错.