The Android Emulator includes a network simulator that lets you develop and test Android apps without using physical radios.
This page describes command-line options for controlling features of the network simulator.
When starting an emulator from the command line, use the -netsim-args flag in
emulator flags to pass arguments to the network simulator.
emulator -netsim-args="arg1 [arg2 ...]"
For example, to enable packet capture, logging, and set a specific HCI port you can use:
emulator -netsim-args="--pcap --logtostderr --verbose --hci-port 12345"
Netsim Configurations
These flags control the general behavior and setup of the netsim daemon.
-l, --logtostderr: Set whether log messages go to stderr instead of log files. Useful for seeing logs directly in the emulator output.-v, --verbose: Enable verbose mode. This mode prints more detailed logs, which is useful for debugging complex issues.--hci-port <HCI_PORT>: Set a custom HCI port. Useful for running multiple emulators or connecting to a specific HCI port.
Specify the directory for artifacts
To specify a directory for the network simulator artifacts, set the environment
variable $ANDROID_TMP:
export ANDROID_TMP=/path/to/your/directory
The network simulator saves the artifacts in the following directory:
$ANDROID_TMP/android/netsimd/. If the environment variable $USER is set, the
network simulator saves the artifacts in $ANDROID_TMP/android{-$USER}/netsimd/
.
Capture Network Packets
To enable packet capture, use the --pcap argument with the emulator.
emulator -netsim-args="--pcap"
This feature is useful for debugging network issues and analyzing traffic. The
network simulator saves a packet capture (pcap) file for each radio chip. You
can open these files with tools like Wireshark. The network simulator saves the
packet capture files in the pcap subdirectory of the netsimd artifacts
directory.
Configure Wi-Fi access point (custom SSID and encryption)
To configure a Wi-Fi access point, use the --wifi argument with the emulator.
For example:
emulator -netsim-args="--wifi <SSID> <PASSWORD>"
SSID: The network name.PASSWORD: The network password is optional and must be 8 or more characters; when set, the access point will be encrypted with WPA2 (CCMP).
Set Received Signal Strength (RSSI)
The network simulator supports setting specific RSSI values for a specific radio
with the --rssi flag.
emulator -netsim-args="--rssi <PHY_KIND:RSSI_VALUE>"
PHY_KIND: The type of Bluetooth radio (e.g.,ble,bt_classic). This parameter supports case-insensitive aliases.RSSI_VALUE: The RSSI value, an i8 (integer).
For example, the following command sets the RSSI for BLE traffic to -65 dBm:
emulator -netsim-args="--rssi=ble:-65"
You can specify this flag multiple times for different radios (e.g.,
--rssi=bt_classic:-65 --rssi=ble:-72).