I ran into this issue as well on my iMac, but since I have dev servers running in a VM all the time, I don't put my machine to sleep, so for me, the problem was fixed by how I am using my Mac. However, I also have a MBP where this problem would crop up every now and then; especially when the MBP would go to sleep.
However, you may wish to try enabling and disabling your network interface (like turning it off and on).
Do the following:
1) Determine name of your ethernet adapter:
en0: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500options=10b<RXCSUM,TXCSUM,VLAN_HWTAGGING,AV>
inet6 fe80::aa20:66ff:fe39:2c1c%en0 prefixlen 64 scopeid 0x4
inet 192.168.10.103 netmask 0xffffff00 broadcast 192.168.10.255
media: autoselect (1000baseT <full-duplex,flow-control>)
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet6 fe80::8e2d:aaff:fe3a:ec83%en1 prefixlen 64 scopeid 0x5
inet 192.168.10.102 netmask 0xffffff00 broadcast 192.168.10.255
Mine is rather long with all the "virtual interfaces" for my VMs and I am using physical 2 ethernet connections and no Airport. So, your mileage may vary. However, for this example, let's use "en0" as our test case. Issue the following commands:
2) Bring down the network interface
$ sudo ifconfig en0 down
<Enter Your Password>
3) Bring the network interface back up
$ sudo ifconfig en0 up
That should restart that device without having to reboot the system.
Another option is to reboot your router. This worked for me as well. I am running DDWRT on my router and it has the ability to schedule a reboot and I configured it to do so every week at 3:00am. I've had zero problems with any of my Macs running 10.10.x. If your router doesn't support "task scheduling" then you will have to do it manually.
Finally, the other alternative is to disallow your Mac to go into sleep/hibernate mode. It's not the most energy friendly option, but in the interim until Apple can get this sorted out, it will save you from a ton of headaches.