Common I/O errors include:

When an I/O error happens, the slave status that we saw in the previous section becomes Slave_IO_Running: No and the reason appears in the Last_IO_Errno and Last_IO_Error fields. The error logfile also contains messages about I/O thread failures if log_warnings is set to 1 (the default).

When the slave cannot connect, the first thing to check is whether the replication user has the correct permissions on the master. The replication user (the user you specify as master_user in the CHANGE MASTER query that begins replication) must have the REPLICATION SLAVE privilege on the master. If it does not, just grant such a privilege to this user on the master.