> >> I tried to ping the server, and it can accept all data. Is there a good way >> to check it? > > ssh -v, ssh -vv and ssh -vvv might give you some interesting information. > Yes, I tried ssh -vvv. It gave a lot of information while login, but it quit without any further information except for “write failed, broken pipe’. >> The problem came out while reinstalling centos 7.7. > > Since you're apparently using some kind of an unofficial or non-standard version of Centos, you might want to try using a current (regular) one instead. > Sorry I made a mistake for the version. I am using v7 instead of v7.7. Thanks, Hua ----------------------------- Hua Wang, Ph.D. in Geodesy Department of Surveying Engineering, Guangdong University of Technology, 100 Waihuan Xi Rd., Panyu District, Guangzhou, 510006, China. Tel: +86-13570019257 Email: ehwang at 163.com Homepage: http://homepages.see.leeds.ac.uk/~earhw