I've been experiencing some difficulties when doing a git push to a repository on my server at home. This would occur when pushing a repository where some binaries needed updating, so there was some need for a lengthier connection than usual (the error occured at just over 20 seconds). The issue would manifest itself as a "Broken Pipe", something like this: 

Connection reset by xx.xxx.xxx.xx port 22
The remote end hung up unexpectedly, 2.40 MiB | 128.00 KiB/s
fatal: sha1 file '<stdout>' write error: Broken pipe
fatal: The remote end hung up unexpectedly

I say "something like" because actually the message was a bit garbled - probably through the stdout and sterr outputting simultaneously to the shell - and I've replaced the IP address with "x"s. 

I Googled for this problem and found enough examples of people suggesting "git config --global http.postBuffer 157286400", which wasn't relevant for me as I was using SSH. (Although I did actually try it - but as expected, it didn't help.)

Then I followed a line of inquiry based on configuring ServerAliveInterval on the client or ClientAliveInterval on the server. Neither of these helped, although at least I had the advantage of being able to control both client and server - a luxury denied most of the people that Google had turned up.

In the end, I reached the point where I was becoming increasingly convinced that my settings were OK, and decided to check if a software update was available for SSHD on my server. As I'm running a Gentoo box, this involved an "emerge --sync", and during this I got a broken pipe. So plainly there was something amiss at a networking level, and along the way the fact that I was connecting via WiFi had just become a lot less relevant, as the server is wired,and also nothing to do with the laptop. 

The laptop in question, from which I was attempting the "git push", was configured to connect to the server using its DNS name, and sure enough, the IP address in the error message was the WAN address of my outermost router; the one provided by the ISP. So I quickly added another git remote, this time using the local address of the server in the 192.168.0.0/24 subnet and sure enough, the "git push" worked like a charm. 

So now the only thing to do is figure out where this is breaking in the network. Meanwhile - if you're struggling with this, maybe your attention needs to be on something other than GIT.... and maybe not. Happy hunting!