Click on Select task button and select BLE Device. 

• Make sure your BLE device is turned on and within range

• Since Android 6 Location (GPS) needs to be enabled for scan to find any devices.

• Click Scan to start searching for BLE devices. All found devices will be added to the list (name and MAC address)

• Click on the device which you want to connect to (scanning is automatically stopped)

• In this example, we want to connect to BLE device MLT-BT05. It was successfully found by a scanner, so we just click on it.

In order to connect to USB-serial device, your smartphone must support USB OTG functionality. You also need USB OTG cable. Supported USB devices are: CP210x, CDC, FTDI, PL2303 and CH34x chips.

Plug in USB-serial converter using USB OTG cable. Click on Select task button and select USB-serial. USB device should be automatically detected. In some cases (some smartphones) more than one USB device can be detected (might be internal USB device). In that case you need to try which one is the correct one by changing index in the drop-down menu USB#.

Following parameters can be set for the connection:

• Baud rate[bps]

• Data bits

• Parity

• Stop bits

• Flow control

After setting up the parameters click on the "USB connect" button. After successful connection, device name will be displayed in the respective Device A or B panel of the main screen and status will be set as "Connected".

Using TCP client, app can connect to a TCP server on a network (local network or internet). Make sure you are connected to the right network. TCP server can be created on a PC, other smartphone device or any other device supporting TCP protocol. If you create TCP server on a PC, make sure firewall is not blocking connections. Alternatively you can connect to a server running on the same device using localhost address. 

To connect to a TCP server, you need to start TCP client in the app. Click on "Select task" button and select TCP client. To connect to a TCP server you need to enter its IP address (or host name) and port number. Click "Connect to Server" and TCP client from your smartphone will connect to specified TCP server.

You can also configure TCP client to try to automatically reconnect if connection is lost. This might be useful in scenarios where a device is moving in and out of a network range or when WiFi signal is weak. This autoreconnection simply tries to re-establish previous connection with configured parameters and is performed each second.

App can start TCP server and allow connection of multiple TCP clients. To start TCP server click on "Select task" button. On next screen following parameters can be configured for the server.

Local Port specifies the port number on which your server will be listening. Your IP address is displayed also, use it on your TCP client together with the port number you specified to make a connection.

Following features are available in PRO version.

Client count limit determines how many client connections will server accept. When the client count is already full and new client tries to connect you can configure server to refuse incoming connection or to disconnect oldest client and allow new incoming connection. This option might be useful if your client loses connection with server (it moves out of WiFi range) and socket is not closed on server side. With this option checked you will be able to re-establish connection without the need of restarting TCP server. No connection will be overwritten in such case, because it was already lost.

In the case that multiple clients are connected to the server, it acts as a multiplexer / splitter. All outgoing data are splited to all clients and all incoming data are multiplexed to one stream for other connected device.

There is also an option to automatically disconnect connected client if no data is coming from it for set period of time. You can specify timeout in seconds. In the example below, connection with the client will be interrupted by TCP server if it receives no incoming data for 10 seconds. Uncheck the checkbox to not use this feature. If multiple clients are connected, this timeout refreshes each time when server receives data from any client. If timeout expires, all clients are disconnected.

App can open listening UDP socket. You can specify local port number. For remote device (remote UDP socket) you need to know and enter its IP address and its port number. 

UDP is connectionless communication - no active connection is created when you create a UDP socket. Data transmitted over network are individually addressed and routed based on information carried in each data packet. Therefore status of this connection (on the main screen) does not differentiate between connected /  disconnected state.

Next connection option is MQTT client. Enter typical parameters, as broker (IP address or its host name), port, connection protocol, QoS, Client ID and publish and/or subscribe topic. Either publish or subscribe topic must be entered. If only publish topic is defined, MQTT client will only send data. If only subscribe topic is defined, MQTT client will only receive data.

You can also specify credentials (username and password) if broker requires authentication. Leave these fields empty to connect without authentication.

Note about QoS parameter: QoS (Quality of Service) is a parameter used in MQTT (Message Queuing Telemetry Transport) protocol to specify the level of guarantee for delivering a message. There are three levels of QoS:

• QoS 0: At most once delivery (fire and forget)

• QoS 1: At least once delivery (acknowledged delivery)

• QoS 2: Exactly once delivery (assured delivery)

QoS 0 is the fastest and least reliable option, while QoS 2 is the slowest but most reliable option. The level of QoS is determined by the publisher and is specified when publishing a message. The subscriber can also request a specific QoS level when subscribing to a topic.

When ready, click Connect to Broker to establish connection.

App can run in background, when minimized or when screen is turned off. To prevent Android OS from stopping app in the background mode, it is highly recommended to have app excluded from battery optimization in phone settings.

Once the device is active or connection established, you can view its current configuration by clicking on its symbol.

When both connections are established (Device A and Device B) app immediately acts as a communication mediator. This is indicated by a status "Bridge active".  All received data from one device are automatically send to the second device and vice versa. However, if needed, this behaviour can be changed. App can act as a one-way filter, re-sending only data from one device to the second, but ignoring incoming data from the second device. To activate this feature select the desired retransmission direction in the Retransmission drop-down menu. If needed, retransmission can also be (temporarily) disabled.

Incoming data from remote devices can be viewed in the log. To show log click on "Traffic" button on the main screen.

To start logging incoming data click on a "Start" button. Data logging is not enabled by default since it can slow down data retransmission (if you use high transfer speeds and large amount of data you might notice a delay when logging is enabled).

In a drop-down menu you can select which data you want to show in log.

• All received data - shows all received data from both connected devices (or from one if only one is connected)

• Transferred data only - shows only data which are retransmissioned from one device to another

Incoming message consist of data identifier (name of a device from which message is received and time stamp of reception) and data itself. Data identifiers can be customised in settings. Size of the font used for logging can be changed in settings also.

In the following screenshot 2 devices are connected (BLE device MLT-BT05 and TCP server) and each is sending data. You can identify sender by its name.

If the color differentiation is enabled in the setting, following colors will be used:

• white for incoming data from device A

• cyan for incoming data from device B

• grey for informational messages

You can also copy a particular message from the log by long clicking on it. It will be copied to a clipboard.

Data can be send to remote devices directly from the app (traffic page). You can select between hexadecimal or text form. To switch between these two options, click on "0x/txt" button. Enter value (either valid hexadecimal number or text) and click "Send". In the checkboxes "A" and "B" you can specify to which connected devices(s) you want to send the data. Data will also appear in the log.

Autostart / autoconnect feature (available only in PRO version) allows you to automatically connect to selected device(s) upon app start without need to selecting it (them) manually each time. Each type of device (connection) can be configured for autostart functionality.

To enable this feature either device A, B or both need to be configured, meaning each required parameter must be known for app to be able to establish connection or start task on next app run.

First thing you need to do is to connect manually (without autostart) to the device(s) which you want to be remembered by autostart function. Then from the app settings open Autostart menu. Here, set currently connected device A, B or both by clicking on "Configure device A/B" and select "Set currently connected device". You can review autostart configuration for both devices by clicking on "View autostart script configurations".

Second step is to enable autostart functionality. Click on "Autostart" and select Enable. Autostart can be enabled only if at least one device(A/B) is configured for autostart.

"Help with autostart" will get you here.

Autostart / Autoconnect feature is carried out by a script which runs automatically (if enabled in settings) when the app starts. This script goes through different steps based on configured device types. For example if Bluetooth device is configured for autoconnect, Bluetooth adapter is checked and enabled (if it is not). Then required permissions are checked, then connection attempt is initiated, etc...

Autostart script runs for device A then device B. If Only one device is configured, other device is skipped.

Autostart script can be interrupted by user. In such case all already established connections will be disconnected.

If needed, autostart script can be run again later, when app is already started by clicking on "Re-run" button. Any active connections will be closed a priory.

To access the app settings click on the 3 lines symbol in the top right corner in the main screen.

• In Screen setting you can set if you want your phone screen to stay always on (with full brightness or dimmed) or if you want it to be turned off (turn off timeout for screen can be changed in Android settings, usually under Display/Sleep options)

• Autostart setting allows to configure automatic connections when app starts. See section above Autostart/Autoconnect.

• Close connections disconnects all remote devices

• IP address detection - select a method for IP address detection. Get_IP - Gets the server IP. Will return 127.0.0.1 (localhost) if no other IP is found. If WiFi network is available this method gets wifi network IP. GetWiFi_IP - Gets the IP address of the WiFi network. Returns 127.0.0.1 (localhost) if not connected.

• Log settings contains advanced settings and customisation options

• How it works - shot instructions, with a link to full user guide.

• About section contains additional information about Bluetooth/USB/TCP app

To exit settings, click on the back button. All changes are saved automatically.

Log settings is accessible via settings menu.

• By changing Font size in log you can adjust text size in the log on the main screen to fit your needs. Valid font size is between 8-20.

• Message identifier data allows to customise data identifier for incoming and outgoing messages. Time stamp contains time of the message reception or transmission.

• Message identifier show lets you customise when you want the message identifier be shown. Options are: never, always and only if sender changes.

• Line break in text mode option allows you to specify how the incoming data are logged. This option only affects data logging when format of incoming messages is set to text.

  • With each new data - fastest option for data logging. Each time data are received, they are inserted as a new line.

  • When carriage return is received (0x0D) OR When line feed is received (0x0A) - Line break is only inserted if selected EOL character is received or if width of log is reached.

• By default text color differentiation is used in main log (separate color used for incoming messages from BLE device and classic Bluetooth devices, outgoing messages and informational messages). This option can be disable in which case only white color will be used for all text in log.

• Message limit in log determines how  many lines can main log hold. If this  limit is exceeded, oldest messages will be automatically removed.  This limit is adjustable within range 100 - 4000 lines.