Can't log in to mysql? May I ask what went wrong?

Question

I installed MySQL before and then a classmate mistakenly deleted the .sock socket file. After adjusting various permissions, MySQL successfully resumed running, but the problem came. Now no matter what command is entered, ERROR 1045 is displayed ( 28000): Access denied for user 'langdan'@'localhost' (using password: NO)，

Then the error log is from Jiang Zi

2017-07-03T09:08:31.486912Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2017-07-03T09:08:31.487319Z 0 [Note] --secure-file-priv is set to NULL. Operations related to importing and exporting data are disabled
2017-07-03T09:08:31.487395Z 0 [Note] /usr/local/mysql/bin/mysqld (mysqld 5.7.18) starting as process 87271 ...
2017-07-03T09:08:31.492488Z 0 [Warning] Setting lower_case_table_names=2 because file system for /usr/local/mysql/data/ is case insensitive
2017-07-03T09:08:31.681427Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2017-07-03T09:08:31.681473Z 0 [Note] InnoDB: Uses event mutexes
2017-07-03T09:08:31.681482Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier
2017-07-03T09:08:31.681492Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.3
2017-07-03T09:08:31.682043Z 0 [Note] InnoDB: Number of pools: 1
2017-07-03T09:08:31.682213Z 0 [Note] InnoDB: Using CPU crc32 instructions
2017-07-03T09:08:31.812247Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
2017-07-03T09:08:31.831267Z 0 [Note] InnoDB: Completed initialization of buffer pool
2017-07-03T09:08:31.902871Z 0 [Note] InnoDB: Highest supported file format is Barracuda.
2017-07-03T09:08:31.923340Z 0 [Note] InnoDB: Creating shared tablespace for temporary tables
2017-07-03T09:08:31.962321Z 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
2017-07-03T09:08:32.631348Z 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
2017-07-03T09:08:32.633295Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active.
2017-07-03T09:08:32.633338Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active.
2017-07-03T09:08:32.633751Z 0 [Note] InnoDB: Waiting for purge to start
2017-07-03T09:08:32.685043Z 0 [Note] InnoDB: 5.7.18 started; log sequence number 2576361
2017-07-03T09:08:32.685414Z 0 [Note] InnoDB: Loading buffer pool(s) from /usr/local/mysql-5.7.18-macos10.12-x86_64/data/ib_buffer_pool
2017-07-03T09:08:32.685622Z 0 [Note] Plugin 'FEDERATED' is disabled.
2017-07-03T09:08:32.686293Z 0 [Note] InnoDB: Buffer pool(s) load completed at 170703 17:08:32
2017-07-03T09:08:32.695242Z 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context is not usable without certificate and private key
2017-07-03T09:08:32.702677Z 0 [Note] Server hostname (bind-address): '*'; port: 3306
2017-07-03T09:08:32.702967Z 0 [Note] IPv6 is available.
2017-07-03T09:08:32.703064Z 0 [Note]   - '::' resolves to '::';
2017-07-03T09:08:32.703210Z 0 [Note] Server socket created on IP: '::'.
2017-07-03T09:08:37.215832Z 0 [Note] Event Scheduler: Loaded 0 events
2017-07-03T09:08:37.216076Z 0 [Note] /usr/local/mysql/bin/mysqld: ready for connections.
Version: '5.7.18'  socket: '/tmp/mysql.sock'  port: 3306  MySQL Community Server (GPL)
2017-07-03T09:08:37.216100Z 0 [Note] Executing 'SELECT * FROM INFORMATION_SCHEMA.TABLES;' to get a list of tables using the deprecated partition engine. You may use the startup option '--disable-partition-engine-check' to skip this check. 
2017-07-03T09:08:37.216108Z 0 [Note] Beginning of list of non-natively partitioned tables
2017-07-03T09:08:40.456702Z 0 [Note] End of list of non-natively partitioned tables
2017-07-03T09:08:40.495603Z 4 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:40.499672Z 3 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:41.989306Z 5 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:43.985722Z 6 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:46.096607Z 7 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:48.291440Z 8 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:50.218176Z 9 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:51.982287Z 10 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:54.586154Z 11 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:56.193629Z 12 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:08:57.986180Z 13 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:09:00.083261Z 14 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:09:02.263890Z 15 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:09:04.464658Z 16 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:09:06.655734Z 17 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:09:08.846245Z 18 [Note] Access denied for user 'langdan'@'localhost' (using password: NO)
2017-07-03T09:09:11.027710Z 

Answer 1

1. Is the password correct? 2. Is the access restricted IP used?