Red Hat Enterprise Linux Server release 7.4 (Maipo)
Microsoft SQL Server 2017 (RTM-CU3-GDR) (KB4052987) - 14.0.3015.40 (X64)
Dec 22 2017 16:13:22
Copyright (C) 2017 Microsoft Corporation Express Edition (64-bit) on
Windows Server 2012 R2 Standard 6.3 <X64> (Build 9600:) (Hypervisor)

[ec2-user@ip-~]$ sqlcmd -H mssqldb.xxxxxxxxxxxxxx.com -P 1433
                        -U userXXXXX -P aXXXXXX
                        -Q 'SELECT TOP 1 [n] FROM [dbbase2].[dbo].[table_people]'

Sqlcmd: Error: Microsoft ODBC Driver 17 for SQL Server :
               Login timeout expired.
Sqlcmd: Error: Microsoft ODBC Driver 17 for SQL Server :
               TCP Provider: Error code 0x2749.
Sqlcmd: Error: Microsoft ODBC Driver 17 for SQL Server :
               A network-related or instance-specific error has occurred while
               establishing a connection to SQL Server. The server is not found
               or not accessible. Check if instance name is correct and if SQL
               Server is configured to allow remote connections. For more
               information see SQL Server Books Online.

[ec2-user@ip- ~]$  Check if instance name is correct and if SQL Server is
                   configured to allow remote connections.