Unable to connect to any services via 127.0.0.1

I logged into a 16.04 server we hadn't touched for months, did an apt-get upgrade and rebooted it.

Now unable to reach anything via 127.0.0.1, e.g.

$ telnet 127.0.0.1 3308
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused

However localhost works e.g.

$ telnet localhost 3308
Trying ::1...
Connected to localhost.
Escape character is '^]'.
_
$B9+/&0X???gbJ:< hDWfM5mysql_native_password

So IPv6 is working, but IPv4 apparently not. Problem is I have a bunch of services trying to connect via IPv4.

Further information:

No, this is not the same as the 16.04 upgrade issue, network access is not a problem.

ifconfig:

eth0 Link encap:Ethernet HWaddr f2:3c:91:e2:e9:e3 inet addr:139.*.*.* Bcast:139.*.*.* Mask:255.255.255.0 inet6 addr: fe80::*:*:*:*/64 Scope:Link inet6 addr: 2a01:*::*:*:*:*/64 Scope:Global UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:420333 errors:0 dropped:0 overruns:0 frame:0 TX packets:427976 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:103142955 (103.1 MB) TX bytes:41541069 (41.5 MB)
eth0:1 Link encap:Ethernet HWaddr f2:3c:91:e2:e9:e3 inet addr:192.168.*.* Bcast:0.0.0.0 Mask:255.255.128.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:46250 errors:0 dropped:0 overruns:0 frame:0 TX packets:46250 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1 RX bytes:48447261 (48.4 MB) TX bytes:48447261 (48.4 MB)
tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:10.5.4.1 P-t-P:10.5.4.1 Mask:255.255.248.0 inet6 addr: fe80::fbaa:a6ee:9adf:f417/64 Scope:Link UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:7859 errors:0 dropped:0 overruns:0 frame:0 TX packets:5347 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:489368 (489.3 KB) TX bytes:1483636 (1.4 MB)

/etc/hosts:

127.0.0.1 localhost
127.0.1.1 hostname.my.domain hostname
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

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