If you want to play against other real people, you need a game server to which all players, including yourself, need to connect. Do that by selecting any other host or by manually entering a new host name and by specifying your password for that host. The last used password will be proposed.
The easiest way is to use the game server at kajongg.org. Kajongg will show this one in the list of possible game servers. Please note that for now kajongg.org only offers a game server but no web page or any other services.
If you do not have an account on the game server with the name you entered, you will be asked if you want to open an account. If you say yes, you will get a new dialog where you can enter the wanted password twice. Your account will be created automatically.
After a successful login onto the game server, you will get a list of tables with available seats on that game server. Join a table or allocate a new table. If you allocate a new table, wait until more seats are taken by other players. You can start the game on a table you allocated at any time, the seats not taken will be filled by robot players.
The table list also shows the name of the ruleset played on that table. The ruleset and its name are sent to the game server by the player initiating the table. If you have an identical ruleset, the table shows your name for the ruleset - this might be helpful if the table initiator speaks another language and named the ruleset differently. Also, if the name of your local ruleset is displayed, it is displayed in black. If however you have no identical ruleset, the name appears in red, and you can use the button to compare it with your own rulesets.
If you do not use kajongg.org or any other existing game server, you can start your own Kajongg game server in two different ways:
connect to the server "localhost". This is your own computer. If you do this and no game server is running, it will be started automatically. And when you stop playing, the server will be stopped too.
manually start a server on any computer you want. All you need to do is go to a command line and start the program
kajonggserver --helpwill show you all available options like changing the default port. This server will run until you kill it.
In both cases you need to tell the other players how they can reach your game server. They need the URL or simply an IP address and the port your server is
listening on. This might be something like
8409 is the port. Of course you need to configure your firewall such that the remote
player can reach that port. The communication will be encrypted.
The server computes its default port from its version number. If Kajongg has version 4.9.5, port 8409 will be used: 8000 plus first version digit * 100 plus middle version digit. If the player enters no port for the wanted game server, the client computes the port in the same way. So if a computer runs several game servers with different program versions, you should normally reach the correct game server automatically. Anyway the game server and the client will make sure that their versions are compatible and warn you otherwise.
If you encounter possible bugs, you might want to use the option
--debug=traffic. This will show you, on the console where the game server has been started,
what messages are flowing between the game server and the clients.
If you want to make sure nobody can cheat none of the human players should have access to the computer the game server is running on. Of course you can never avoid that two players help each other because you cannot know what they really are doing. Two players might even be one and the same person.