What does CN mean in aria2 downloading info?

Solution 1:

man aria2c has this way down starting on line 2480:

MISC

Console Readout

While downloading files, aria2 prints the console readout to tell the progress of the downloads. The console readout is like this:

[#2089b0 400.0KiB/33.2MiB(1%) CN:1 DL:115.7KiB ETA:4m51s]

This section describes what these numbers and strings mean.

  #NNNNNN
         The first 6 characters of GID in hex string. GID is an unique ID for each download.

  X/Y(Z%)
         Completed length, the total file length and its ratio. If --select-file is used, this  is  the  sum  of  selected file.

  SEED   Share  ratio.  The  client  is now seeding. After BitTorrent download finished, size information is replaced with this.

  CN     The number of connections the client has established.

  SD     The number of seeders the client is now connecting to.

  DL     Download speed (bytes per second).

So, CN is "The number of connections the client has established.