Containers can't communicate on my user-defined network

General
1

I fired up two containers like this:
docker run -d -p 10001:80 --name blog1 tutum/wordpress
docker run -d -p 10002:80 --name blog2 tutum/wordpress

Then created a network:
docker network create my_network

Then connected my two containers to the network:
docker network connect my_network blog1
docker network connect my_network blog2

Then I fired up a third container and connected it to my network:
docker run -it --network my_network ubuntu:16.04 bash

I installed curl on the ubuntu container and tried to query the first 5 lines of blog1’s HTML:
curl -sSL blog1 | head -n5

I got this error:
curl: (7) Failed to connect to blog1 port 10001: Connection refused

Why did blog1 refuse the connection?

When I ran ‘docker network inspect my_network’ it shows all three containers on the same network:

[
    {
        "Name": "my_network",
        "Id": "fd48da51d2da0fd5c5f9a9a879d4677d2b8bda9a7a33ca984a6a29efc9b01716",
        "Created": "2021-03-18T16:30:37.3796504Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.18.0.0/16",
                    "Gateway": "172.18.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "710c502acd8e5535b99a7b7f9951ed768586c42b9b905833dee03a9829e912d0": {
                "Name": "blog2",
                "EndpointID": "86a766a6136e3b247a8991368c77d94a1fd63465128e7524e2735f3ec0f24575",
                "MacAddress": "02:42:ac:12:00:04",
                "IPv4Address": "172.18.0.4/16",
                "IPv6Address": ""
            },
            "c22323fd24ddcfd0d871e53e755545323f2822dd1ab214f4a81862a971e88351": {
                "Name": "romantic_payne",
                "EndpointID": "2262bf054e5b74dc04a97e4e795d75a0148fc2a465828e6bd3c95ab8ea60629a",
                "MacAddress": "02:42:ac:12:00:03",
                "IPv4Address": "172.18.0.3/16",
                "IPv6Address": ""
            },
            "d875536ede1182126d325290bdb01fc000b8a5e9944992f0b28f090cbc916ede": {
                "Name": "blog1",
                "EndpointID": "f783e8bd629d875f3125017faeae3ff59dd4c2e9c81b08452b41247f64856bd0",
                "MacAddress": "02:42:ac:12:00:02",
                "IPv4Address": "172.18.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]