added attach over ipc command

rpc/comms/ipc_unix.go

@@ -18,7 +18,17 @@ func newIpcClient(cfg IpcConfig, codec codec.Codec) (*ipcClient, error) {
 		return nil, err
 	}
 
-	return &ipcClient{codec.New(c)}, nil
+	return &ipcClient{cfg.Endpoint, codec, codec.New(c)}, nil
+}
+
+func (self *ipcClient) reconnect() error {
+	self.coder.Close()
+	c, err := net.DialUnix("unix", nil, &net.UnixAddr{self.endpoint, "unix"})
+	if err == nil {
+		self.coder = self.codec.New(c)
+	}
+
+	return err
 }
 
 func startIpc(cfg IpcConfig, codec codec.Codec, api api.EthereumApi) error {