like
function serverCmdNameofcommand(,'',%client)
Do i leave that part as client?
No. messageAll messages all the clients in the game and there is no need to pass a client argument.
However, the messageAllExcept(); function lets you send a message to everyone except a specified client, and in that case you do need to pass a client variable. For example,
$client = findclientbyname("bob");
messageAllExcept($client, '', '\c6Everyone except Bob can see this message.');
Also, in serverCmd functions, the client variable is the first argument passed.
function serverCmdNameofcommand(,'',%
client) is incorrect.
function serverCmdNameofcommand(
%client, %whatever, %stuff, %you, %want) is the way to go.