torrent network checking and New file encounter notification

[ucwong]

No description provided.

[codecov]

Codecov Report

Merging #834 (2bf40d4) into master (9ec11e8) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #834      +/-   ##
==========================================
- Coverage   49.12%   49.09%   -0.03%     
==========================================
  Files         418      418              
  Lines       47771    47771              
==========================================
- Hits        23467    23454      -13     
- Misses      22247    22273      +26     
+ Partials     2057     2044      -13     

Impacted Files	Coverage Δ
params/version.go	36.84% <ø> (ø)
ctxc/downloader/statesync.go	55.29% <0.00%> (-6.67%)	⬇️
p2p/discover/v4_udp.go	72.91% <0.00%> (-4.33%)	⬇️
whisper/whisperv6/whisper.go	50.40% <0.00%> (-1.43%)	⬇️
p2p/peer.go	76.71% <0.00%> (-1.06%)	⬇️
ctxc/downloader/downloader.go	77.01% <0.00%> (+0.10%)	⬆️
p2p/discover/v5_udp.go	81.67% <0.00%> (+0.53%)	⬆️
core/tx_pool.go	76.27% <0.00%> (+0.77%)	⬆️
p2p/server.go	65.95% <0.00%> (+0.85%)	⬆️
trie/proof.go	74.54% <0.00%> (+1.09%)	⬆️
... and 3 more