Ubuntu 关闭了 ufw， iptables 也没有限制，能 ping 通但是不能访问端口，应该怎么排查

之前主要用 CentOS ，一般就是修改 /etc/selinux/config 和关闭 firewalld 。

最近换到了 Ubuntu 20.04 ，做了如下设置。

IP：

xxx@xxx:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 04:bf:1b:80:06:4b brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.26/16 brd 192.168.255.255 scope global noprefixroute enp3s0
       valid_lft forever preferred_lft forever
    inet6 fe80::b31c:c7f4:6bca:b597/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: wlp0s20f3: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 74:3a:f4:68:ab:50 brd ff:ff:ff:ff:ff:ff
4: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    link/ether 02:42:9f:c4:78:0b brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:9fff:fec4:780b/64 scope link 
       valid_lft forever preferred_lft forever
6: veth5f39922@if5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP group default 
    link/ether ba:ba:dd:9b:cc:03 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet6 fe80::b8ba:ddff:fe9b:cc03/64 scope link 
       valid_lft forever preferred_lft forever

关闭 ufw：

sudo ufw disable
sudo systemctl stop ufw
sudo systemctl disable ufw

sudo iptables -P INPUT ACCEPT
sudo iptables -P FORWARD ACCEPT
sudo iptables -P OUTPUT ACCEPT
sudo iptables -F
sudo netfilter-persistent save

Ubuntu 上启动了一个 fastapi 的项目，本机通过 localhost 或者 ip 都可以访问。 现在内网其他设备可以 ping 通 Ubuntu ，但是所有端口都无法访问，请问可能是什么原因或者如何排查？