build.gradle

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.0.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

task find_ipaddress(type: Exec) {
    commandLine '/bin/bash', '-c', 'ifconfig | grep "inet " | grep -v 127.0.0.1 | cut -f2 -d\\ '
    standardOutput = new ByteArrayOutputStream()

    doLast {
        print "My IP is " + standardOutput.toString()
        project.ext.my_ip = standardOutput.toString()   
    }
}

task open_website() {
    dependsOn find_ipaddress
    doLast {
        def my_url = "'http://${project.ext.my_ip}:8887/index.html'"
        exec {
            if (System.properties['os.name'].toLowerCase().contains('windows')) {
                // windows
                commandLine 'cmd', '/c', 'adb', 'shell', 'am', 'start', '-a', 'android.intent.action.VIEW', '-d', my_url
            } else {
                // linux 
                commandLine 'adb', 'shell', 'am', 'start', '-a', 'android.intent.action.VIEW', '-d', my_url
            }
        }
    }
}