Net.OpenConnection

If successful, Net.OpenConnection returns a network stream descriptor which can be used with the put, get, read, and write statements and eof function to send and receive data to the listening program. It is also the parameter used for the Net.CloseConnection, Net.BytesAvailable, Net.CharAvailable, Net.LineAvailable, and Net.TokenAvailable functions.

The netAddr parameter is a string specifying the net address of the machine to be connected to. This can either be the full hostname or the numerical address.

In general, system program listen in on ports with numbers below 1024. Port numbers above 1024 are generally available for use by user created programs.

The program will wait for an indeterminate amount of time to make the connection. If it fails, it will return a non-positive value.

It is possible for Firewalls to interfere with the actions of the Net module, preventing connections from taking place.

        % The "Chat" program
        const chatPort : int := 5055
        var choice : int
        loop
            put "Enter 1 to run chat server"
            put "Enter 2 to run chat session"
            put "Choice: " ..
            get choice
            exit when choice = 1 or choice = 2
        end loop
        var netStream : int
        var netAddress : string
        
        if choice = 1 then
            netStream := Net.WaitForConnection (chatPort, netAddress)
        else
            put "Enter the address to connect to: " ..
            get netAddress
            netStream := Net.OpenConnection (netAddress, chatPort)
            if netStream <= 0 then
                put "Unable to connect to ", netAddress
                return
            end if
        end if
        Draw.Cls
        put "Connected to ", netAddress
        
        var localRow : int := 2
        var localCol : int := 1
        var remoteRow := maxrow div 2
        var remoteCol : int := 1
        var ch : char
        
        View.Set ("noecho")
        loop
            if hasch then
                ch := getchar
                put : netStream, ch
                if ch = '\n' then
                    localRow := localRow mod (maxrow div 2) + 1
                    localCol := 1
                    Text.Locate (localRow, localCol)
                    put "" % Clear to end of line
                    Text.Locate (localRow, localCol)
                else
                    Text.Locate (localRow, localCol)
                    put ch ..
                    localCol += 1
                end if
            end if
        
            if Net.CharAvailable (netStream) then
                get : netStream, ch
                if ch = '\n' then
                    remoteRow := remoteRow mod (maxrow div 2) +
                        1 + (maxrow div 2)
                    remoteCol := 1
                    Text.Locate (remoteRow, remoteCol)            put ""  % Clear to end of line
                    Text.Locate (remoteRow, remoteCol)
                else
                    Text.Locate (remoteRow, remoteCol)
                    put ch ..
                    remoteCol += 1
                end if
            end if
        end loop

This means that you can only call the function by calling Net.OpenConnection, not by calling OpenConnection.