Android Question Error UDP multi socket

[Mr Blue Sky]

Hello everyone,
a little bit of understanding with UDP
I use two UDP ports
the first fixed 52830 listens
the second parametrable between 49152 and 65535 sending (Main.UDPport)
my code is the following:

Sub Class_Globals
    Dim Response, Error As StringBuilder
    Dim UDPSocketReceived As UDPSocket
    Dim UDPSocketSend As UDPSocket
End Sub

Public Sub Initialize
    If Main.checked1 = True Then
        UDPSocketReceived.Initialize("UDP", 52830, 8000)
    End If
 
    If Main.checked2= True Then
        UDPSocketSend.Initialize("UDP", Main.UDPport, 8000)
    End If
End Sub

Sub UDP_PacketArrived (Packet As UDPPacket)
    Dim msg As String
    msg = BytesToString(Packet.Data, Packet.Offset, Packet.Length, "UTF8")
    log(msg)
End Sub

Sub UDP_SendPacket(Checked As String)
        UDPSocketReceived.Close
        UDPSocketSend.Initialize("UDP", Main.UDPport, 8000)
     
        Dim Packet As UDPPacket
        Dim data() As Byte
        data = Checked.GetBytes("UTF8")
        Packet.Initialize(data, Main.UDPhost, Main.UDPport)
        UDPSocketSend.Send(Packet)
     
        UDPSocketSend.Close
        UDPSocketReceived.Initialize("UDP", 52830, 8000)
End Sub

netconnect_initialize (java line: 105)
java.net.BindException: bind failed: EADDRINUSE (Address already in use)
at libcore.io.IoBridge.bind(IoBridge.java:99)
at java.net.PlainDatagramSocketImpl.bind(PlainDatagramSocketImpl.java:60)
at java.net.DatagramSocket.createSocket(DatagramSocket.java:159)
at java.net.DatagramSocket.<init>(DatagramSocket.java:80)
at anywheresoftware.b4a.objects.SocketWrapper$UDPSocket.Initialize(SocketWrapper.java:444)
at com.bmwk100.dashboard.netconnect._initialize(netconnect.java:105)
at com.bmwk100.dashboard.main._vvvvvvvvvvvvvvvvvvvvvv4(main.java:1336)
at com.bmwk100.dashboard.main._vvvvvvvvvvvvvvvvvvvvv3(main.java:1193)
at com.bmwk100.dashboard.main._activity_create(main.java:515)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:191)
at com.bmwk100.dashboard.main.afterFirstLayout(main.java:104)
at com.bmwk100.dashboard.main.access$000(main.java:17)
at com.bmwk100.dashboard.main$WaitForLayout.run(main.java:82)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5538)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:958)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:753)
Caused by: android.system.ErrnoException: bind failed: EADDRINUSE (Address already in use)
at libcore.io.Posix.bind(Native Method)

I get the used address error "used" while I seem to close the sockets and the ports are different

 

[Mr Blue Sky]

well I settled the problem finally
1) it was not worth creating a second socket and initialized it
2) No need to close the receiving socket before the transmission.
It works but it's still not clear in my mind what socket.close serves in the end?

Sub Class_Globals
    Dim Response, Error As StringBuilder
    Dim UDPSocket1 As UDPSocket
End Sub

Public Sub Initialize
    If Main.checked1 = True Then
        UDPSocket1.Initialize("UDP", 52830, 8000)
    End If
End Sub

Sub UDP_PacketArrived (Packet As UDPPacket)
    Dim msg As String
    msg = BytesToString(Packet.Data, Packet.Offset, Packet.Length, "UTF8")
    log(msg)
End Sub

Sub UDP_SendPacket(Checked As String)
        Dim Packet As UDPPacket
        Dim data() As Byte
        data = Checked.GetBytes("UTF8")
        Packet.Initialize(data, Main.UDPhost, Main.UDPport)
        UDPSocket1.Send(Packet)
End Sub

 

[Erel]

It works but it's still not clear in my mind what socket.close serves in the end?

You should call it if you want to close the socket => the socket is no longer needed for your app.

It is fine never to call Close and let the OS close it when the app is killed.

 

[Mr Blue Sky]

Thank Erel,
I use it when I leave the application ?

 

[Erel]

As I wrote, you can keep the socket open and never close it. It will be closed when the OS kills the process.