TCP/IP connection

[Rusty]

I am installing new Android units within a fire-walled environment. This environment is not able to go "outside" to other TCP or FTP locations, so I cannot have a "home base" address.

The site has a PC server with a TCP program running as server.
Other than having the user type in the IP address and port, is there a way for the clients (Androids) to find the server (PC).
Thanks in advance.
Rusty

 

[njesus]

probably with a broadcast (discovery) message that the pc server replies.

in case you don't know how to do it, here it is:

1. discover the broadcast address of your subnet (see here: http://www.shunsoft.net/ipcalc/help/chap07.html)

2. send a udp package to this address and port i.e. 37859

3. have your PC server listen to this udp port. once it detects the package, it'll know it's source (android device). it then starts informs this address it's own address by sending another predefined package to it, preferably a tcp one in another port.

4. android device receives the package, then it'll know where's the PC server.

 

[Rusty]

Great suggestion!
Any chance you have a b4a source code sample of how UDP works?
Thanks,

 

[njesus]

no I don't have one, but I imagine it'd be easy, and probably anyone will chip in with an example. good luck.

 

[Erel]

There is a simple example here:
Basic4android - Network

 

[Rusty]

Thank you once again Erel, you are always very helpful.
I implemented your example and it works beautifully.
I broadcast on 255.255.255.255 and multiple Android devices receive the datagram.
I am having a bit of trouble in the packet data in the UDP_PacketArrived

Sub UDP_PacketArrived (Packet As UDPPacket)
    Dim msg As String
    msg = BytesToString(Packet.Data, Packet.Offset, Packet.Length, "UTF8")
    Msgbox("Message received: " & msg, "")
    Dim parts() As String = Regex.Split("~", msg)
    Dim IPAddress As String = Packet.Host
    Dim IPPort As String = packet.Port

The Dim IPAddress as string = Packet.Host has a threading issue.
Can you advise?
Thanks in advance.
Rusty

 

[Erel]

Use the code here instead to get the IP address:
http://www.b4x.com/forum/119918-post5.html

This method will be marked as deprecated in the next update. It can only be used if you remove android:targetSdkVersion="14" from the manifest editor.

 

[Rusty]

Thanks Erel,
Works great.
However, once deprecated, what will be the recourse?
Also, it returns the IP address of my ethernet adapter instead of the wireless adapter. Is there a way to change this?
The UDP software shows the IP address of 192.168.1.148 (wireless) and the GetHostAddress returns 192.168.1.9 (ethernet). It returns .9 instead of .148.
Thanks,

 

[Erel]

However, once deprecated, what will be the recourse?

Nothing will happen. Users should just avoid using this method as it will throw an error (the one you saw).

GetHostAddress returns the address from the packet. There is only one such address.