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I'm curious to know if there are a maximum number of simultaneous SSH connections into my RPi. I've connected to it twice at the same time, but is there any theoretical limit for the number of connections, besides the bandwidth of the ethernet 100 Mbps (rocking a Pi B+)? I'd be interested to read relevant info, or if anyone has ever reached the maximum, I'd love to hear about it!

Cheers

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    I often have three ssh terminal windows open between laptop and Pi. You could just open hundreds of windows to see if you can find a limit. – joan Jul 25 '18 at 17:25
  • Haha, I'd definitely be taking off authentication for that test. – RJP Jul 25 '18 at 17:25
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man sshd_config has the answer to your question (in a manner of speaking) in the line: MaxStartups 10:30:100, which is the default. Here's another reference that provides additional details.

So it would seem that the maximum number of simultaneous connections is determined by the last value in MaxStartups: 100 in the default case. As far as a connection limit, that would be based on the data type used in the sshd code that holds these values. I think it's a unsigned short int (65,535 max connections), but I'd need to research that to be certain.

Finally, if by theoretical limit you mean, "What will the hardware support?", I'd have to guess the only answer is, "it depends"... depends on how much data each SSH connection is passing, and other loads on the RPi that will compete for processor and memory resources.

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