How to Replicate 2 windows servers

I'm going conditionally disagree with Cliff.

Replicating two PHYSICAL servers is EXTREMELY expensive.  You can use a third party product like DoubleTake or NeverFail.  (You're talking mid-4 figure or more price range) or you can use the specifically designed SQL replication capabilities (not sure if Express will be adequate - if not, you'd be talking about an expensive SQL server license).

Now if this network was designed well, and the servers are virtualized (using Hyper-V), you can use Hyper-V replica free of license costs.  (MIGHT require an additional server license and SQL license - though Volume Licenses should be transferrable once every 90 days - by which logic says to me, you can replicate and even fail over, but you can't fail back for 3 months UNLESS you buy new licenses so that TECHNICALLY, you're not failing back, your switching to another license.

Now the conditional part of my comment - If you're not ADEPT at SQL and you don't FULLY understand what's going on with Replication and the like, then you could be putting yourself at serious risk of data loss.  Think about it - if you ever so much as test and have a transaction go to the secondary server instead of the primary, that data is likely lost.  Further, Replication is NOT instant.  Even replica could lose data (in theory only 30 seconds at it's most frequent replication rate - but you can do a lot in 30 seconds... Orders could be lost, users could be lost, inventory could be lost... lots of bad things.  THIS is why Microsoft doesn't want you replicating without using the appropriate SQL Server based technologies that make such losses least likely to occur.

To be fair Lee, the OP did say:

"How can i achieve real time replication between the 2 Server, so if change is made on either one"

The catch there is "real time." hyper-v replica doesn't fit that request. And the newer storage replica technologies on windows do real-time but aren't application aware. The only way to get real-time replication with a SQL server is within SQL server itself. In case you missed that part of their request.

Yep, did miss the real time part.  Although I'd add that Storage replica requires VERY FAST links and VERY LOW latency.  30 Mb Metro Ethernet wouldn't cut it.  Direct fiber would... but that's expensive too.

Thank you guys for such helpful insights.
Virtualising  is an option. Vmware is currently used not HyperV.
Cost is a major factor.  Though nice to know about (DoubleTake or NeverFail)

As REAL TIME objective cannot be met using  using the current infrastructure and the cost involved. what is next best alternative in terms or simplicity and cost.
Replicate  One Server on Nightly Basis and keep it as DR ? we only have around 70 Users.

i was just checking out the Free VEEAM application and after reading and watching few YouTube Videos, seems to be a good replication option.

Thank you all for your time and effort. Much appreciated

Further information - I just ran across this:
https://support.microsoft.com/en-us/help/956893/support-policy-for-microsoft-sql-server-products-that-are-running-in-a

SQL Server on Hyper-V Replica is supported provided the EnableWriteOrderPreservationAcrossDisks flag is set.

Note To set the EnableWriteOrderPreservationAcrossDisks flag, run the following cmdlet:

Set-VMReplication -VMName <vm-name> -EnableWriteOrderPreservationAcrossDisks 1

Exceptions

If multiple SQL VMs are tightly coupled with one another, individual VMs can failover to the disaster recovery (DR) site but SQL high availability (HA) features inside the VM need to be removed and re-configured after VM failover. For this reason, the following SQL Server features are not supported on Hyper-VM Replica:

    Availability Groups
    Database mirroring
    Failover Cluster instances
    Log shipping
    Replication