Wireless errors when you don't have wireless

[tobyweston]

The start.sh, start-client.sh and start-server.sh script is geared up for wireless connections.

When the server starts up, it attempts to get the IP address of of the machine so you can monitor stats via the JMX console.

It does this with the following line:

IP=$( ifconfig wlan0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}' )

If you don't have a wlan0 configured, this won't work and you'll get an error similar to the following:

wlan0: error fetching interface information: Device not found

[tobyweston]

You should be able to locate the name of your network interface with ifconfig -a, my ethernet is en0 but you're may differ.

As a workaround, you can substitute wlan0 with your network interface name (en0 above) in the start-XXX.sh files. Note this is a unix bash script and may not work on Mac for example. Failing that, you can modify the scripts to just drop the JMX stuff:

#!/usr/bin/env bash

nohup java -Xmx512m -jar target/scala-2.12/temperature-machine-2.0.jar > temperature-machine.log 2>&1 &

echo "$!" > temperature-machine.pid

echo "Started your temperature-machine, redirecting output to temperature-machine.log, PID stored in temperature-machine.pid"

[tobyweston]

To fix this properly, we should check for the existence of network interfaces in some sort of sequence (eth0 then wlan0?) and setup JMX if found, bypass JMX otherwise.

[tobyweston]

The current scripts use the following to assign a value to IP, then uses it later on:

IP=$( ifconfig wlan0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}' )

But we could do something like this.

grep "wlan0" /proc/net/dev

in the script:

#!/bin/bash
WLAN=`grep "eth0:\|wlan0" /proc/net/dev`

if  [ -n "$WLAN" ] ; then
   JMX_OPTS="-D..."
else
   JMX_OPTS=""
fi

ifconfig seems to have changed it's output in recent kernels, so grep'ing inet addr doesn't seem to work of 4.9.58. Might need something like this instead.

ip -f inet addr show wlan0 | grep -Po 'inet \K[\d.]+'

On 4.9.58:

$ ifconfig
wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.1.26  netmask 255.255.255.0  broadcast 10.0.1.255

On 4.1.19:

$ ifconfig
wlan0     Link encap:Ethernet  HWaddr 00:e0:4d:02:1d:f8  
          inet addr:10.0.1.35  Bcast:10.0.1.255  Mask:255.255.255.0

The ip -f command works on both.

[tobyweston]

0bd4c16 should avoid this in the future, this is for inclusion in the 2.1 release so isn't available to test yet but fixes #16 (@lhalep let me know if you want to test but I'll close this once I've merged into mainline)