I've been confronted by the same issue since Nov. 7 (just few days before the Third Plenary Session of 18th CPC Central Committee) with a dozen of clients lost connections in Shanghai. Adding predefined hosts would help but didn't work for WAN. -----Here is the translation of some part of advice by Staalu written in Chinese above which I think inspiring----- Seemingly the issue is due to the block of track servers by the Great Firewall (GFW) for BTSync has been detected for some bypassing behavoiurs. At present we don't have much to do but could only wish GFW removed the block. Hopefully in the future I wish BTSync would make its tracker servers open or enable some full-control secret clients to build their own tracker by embedding this function into the software. Also I hope in the future users could determine which secret goes to which tracker so it would be stronger against the GFW.