Total amount of nodes and avarage active peer number I have 2 questions:


Does anyone know where to find a reliable source for finding out a total amount of active bitcoin nodes?
How many peers does each active node have in avarage? Is there a limit to how many peers one node can have?
Does anyone know where to find a reliable source for finding out a total amount of active bitcoin nodes?


http://getaddr.bitnodes.io/ tracks listening peers on IPv4 and IPv6 only. The number is subject to gaming if people desire, there's no assurance that any of the nodes there are actually useful to connect to. At least some of the nodes listed will be duplicate due to them having both an IPv4 and IPv6 socket open at the same time and thus appearing as "two" nodes.


  How many peers does each active node have in average? 


Bitcoin nodes will only attempt outgoing connections which are in ranges of IP addresses that are not close together, specifically for IPv4 it won't connect to any two nodes that are in the same /16 block. This means that any node running on a popular area such as a VPS host or EC2 node will likely see substantially less incoming activity than one running in a less densely populated area. This is an attempt to raise the cost of a large scale sybil attack against the network by increasing the diversity of IP addresses needed to gain an extremely large number of connections.

As a result you have to be very careful how you gain statistics about the number of incoming connections, because not all listening sockets are equal in the eyes of a client attempting to find peers. As far as I am aware nobody does this sort of data collection on a wide scale and publishes the results, but it is probably in the high tens of connections inbound on most nodes judging by my own experience. 


  Is there a limit to how many peers one node can have?


The default is 125 maximum, 8 outgoing and 117 incoming. 

Absent this the number is bounded by the constraints of the system it is running on.