Unstable Bitcoin Connection

I fork bitcoin core 16.0 and create my own alt coin. I run two bitcoind:

Code:

sudo ~/bitcoin/src/bitcoind -addnode=127.0.0.1:9332 -port=8963 -rpcport=8962 -debug=rpc -dns=0 -dnsseed=0

sudo ~/bitcoin/src/bitcoind -datadir=$HOME/.bitcoin2 -addnode=127.0.0.1:8962 -port=9333 -rpcport=9332 -debug=rpc -dns=0 -dnsseed=0

However, the connection between them seems very unstable. When I use bitcoin-cli -getinfo, sometimes the connection=0

I run locally, So I think the connection should be pretty stable? What's wrong?

Thank you very much.