Install the client with the one-line installer (the server is curl -fsSL https://seikan.okonomi.cloud/server/install.sh | sudo bash on your public host — see the install guide):

# 0. install the client (no root needed)
curl -fsSL https://seikan.okonomi.cloud/client/install.sh | bash

# 1. configure the client once (saved to ~/.config/seikan/config.json)
seikan init --server admin.example.com --api-key sk_...

# 2. expose local :3000 on an HTTPS domain (DNS for app.example.com must point at the server)
seikan serve app.example.com 3000
#    -> https://app.example.com is now live

# 3. or expose a local TCP service on an auto-assigned public port
seikan serve --tcp 5432 --name postgres