[bug] TCP tunnel breaks after every request

[diyism]

==============Server side, firewall only open TCP 4001=========
$ ipfs version
ipfs version 0.4.15

$ ipfs id
"ID": [my vps ipfs id]
$ ipfs p2p listener open p2p-test /ip4/127.0.0.1/tcp/8081
{"Address":"/ip4/127.0.0.1/tcp/8081","Protocol":"/p2p/p2p-test"}

$ curl --socks5 127.0.0.1:8081 http://myip.ipip.net
IP：[my vps wan ip] amazon.com

==================Client side, symmetric NAT===========
$ ipfs version
ipfs version 0.4.15

$ ipfs p2p stream dial [my vps ipfs id] p2p-test /ip4/127.0.0.1/tcp/10102
{"Address":"/ip4/127.0.0.1/tcp/10102","Protocol":"/p2p/p2p-test"}

$ ipfs p2p stream dial [my vps ipfs id] p2p-test /ip4/127.0.0.1/tcp/10102
Error: listen tcp4 127.0.0.1:10102: bind: address already in use

$ curl --socks5 127.0.0.1:10102 http://myip.ipip.net
IP：[my vps wan ip] amazon.com

$ curl --socks5 127.0.0.1:10102 http://myip.ipip.net
curl: (7) Failed to connect to 127.0.0.1 port 10102: Connection refused

$ ipfs p2p stream dial [my vps ipfs id] p2p-test /ip4/127.0.0.1/tcp/10102
{"Address":"/ip4/127.0.0.1/tcp/10102","Protocol":"/p2p/p2p-test"}

$ curl --socks5 127.0.0.1:10102 http://myip.ipip.net
IP：[my vps wan ip] amazon.com

$ curl --socks5 127.0.0.1:10102 http://myip.ipip.net
curl: (7) Failed to connect to 127.0.0.1 port 10102: Connection refused

$ ipfs p2p stream dial [my vps ipfs id] p2p-test /ip4/127.0.0.1/tcp/10102
{"Address":"/ip4/127.0.0.1/tcp/10102","Protocol":"/p2p/p2p-test"}

$ curl --socks5 127.0.0.1:10102 http://myip.ipip.net
IP：[my vps wan ip] amazon.com

$ curl --socks5 127.0.0.1:10102 http://myip.ipip.net
curl: (7) Failed to connect to 127.0.0.1 port 10102: Connection refused

....

What a pity, TCP tunnel breaks after every request.

#3397 (comment)

[magik6k]

This is/was by design, but is being changed as a part of #4929 / #4895 (comment)