Today, I encountered a series of errors in connecting Oracle database with SQL Developer, which took a lot of time and was finally solved. Now I am writing it down, hoping to give some help to those students who encountered the same mistakes
Make sure that both services are started, or if not, start both services first.

The first is this exception Io exception: The Network Adapter could not establish The Connection, this exception is probably The IP error of The host name of The connection, The host name does not have to be localhost or 127.0.0.1, but should be consistent with The IP name in The Oracle installation directory (my name is The directory H:\app\LBJ\ Product \11.2.0\dbhome_1\ Network \ADMIN) listens. ora file. That is, the IP after HOST in the figure below is consistent

After the modification is completed, restart the Listener service (namely the two services in the figure above), and encounter the Listener union connection with the following error: Ora-12505, TNS: Listener does not currently know of SID Given in Connect Descriptor; after searching the data, it is found that there is a problem with SID. The name in the SID is also not optional. It should be the same as the SID_NAME in the file (listlisteners. Ora) (orcl in this case)

      

Restart the listening service after the modification to see if the problem has been resolved. Again, I encountered an error where I was unable to get more information from the socket. Ora file, as shown in the figure above. Simply comment out the #(PROGRAM = extproc) line and the problem is solved. Now restart the service again and find that you can finally connect, and you’re done.