各类型描述如下:
1 Socket is disconnected/closed or file is closed. 2 In non-blocking socket mode, there is no data ready for retrieval yet. 3 Out of memory, no disk space, or no buffer for sending data in non-blocking socket mode. 4 String size exceeds 64K or code size exceeds 1 MB during serialization over network. 5 In non-blocking socket mode, a program is in pending connection mode. 6 Invalid message format. 7 Reach the end of a file or a buffer. 8 File is readable but not writable. 9 File is writable but not readable. 10 A file doesn't exist or the socket destination is not reachable. 11 The database file is corrupted. 12 Not the leader node of the RAFT protocol. 13 Unknown IO error.