can not be reached or does not exist "Database Mirroring"

Dear Friends,

I am trying to configure mirroring between two servers without witness server. Both servers have configured default instance

(MSSQLSERVER). I am configuring the mirroring settings but when clicking to start its giving me this one error:

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TITLE: Database Properties
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An error occurred while starting mirroring.
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ADDITIONAL INFORMATION:
Alter failed for Database 'JI-TFS-Warehouse'.  (Microsoft.SqlServer.Smo)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.50.1600.1+((KJ_RTM).100402-1539+)&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Alter+Database&LinkId=20476

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An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)

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The server network address "TCP://MIRROR.corp.aaj.com:5022" can not be reached or does not exist. Check the network address name and that the ports for the local and remote endpoints are operational. (Microsoft SQL Server, Error: 1418)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.50.1600&EvtSrc=MSSQLServer&EvtID=1418&LinkId=20476

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I can see this error in event viewer window as follow:

Database mirroring connection error 4 'An error occurred while receiving data: '10054(An existing connection was forcibly closed by the remote host.)'.' for 'TCP://MIRROR.corp.aaj.com:5022'.

From principle: If connecting with server (mirror) without instance name then its connecting but if mentioning instance name like mirror\MSSQLSERVER then its not connecting.

Regards