Fix DB Network Adapter could not establish

Fist, make sure you configure listener.ora correctly:

# listener.ora Network Configuration File: C:\Oracle\Database\product\11.2.0\dbhome_1\network\admin\listener.ora
# Generated by Oracle configuration tools.

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = CLRExtProc)
      (ORACLE_HOME = C:\Oracle\Database\product\11.2.0\dbhome_1)
      (PROGRAM = extproc)
      (ENVS = "EXTPROC_DLLS=ONLY:C:\Oracle\Database\product\11.2.0\dbhome_1\bin\oraclr11.dll")
    )
  )

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = 301KhiemTT-W7)(PORT = 1521))
    )
  )

ADR_BASE_LISTENER = C:\Oracle\Database

Run lsnrctrl start to start Listener.

Hope that help!