Send to and receive from sockets.
Send the command cmdNr and the message message to channel channelName using the flags flags. The command numbers are application specific. If #flags is used, flags is the numeric (integer) representation of the flags is to be set. If the # is omitted, flags is a list of symbolic flags. Currently, there is only one flag: multiple or noflush with the same meaning, indicating that there is more to follow and no automatic flush on the channel should be done.
Receives a message from channelName. The other arguments are the names of the corresponding variables which will contain the message. The flags are returned numeric. (To handle these flags, use the web::msgflag function).