Another failed attempt

build.gradle

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.0'
    }
}

allprojects {
    apply plugin: 'idea'

    group = 'org.jfrog.example.bintray.gradle'
    version = '1.2-gradle-publish'
}

subprojects {
    apply plugin: 'java'
    apply plugin: 'maven-publish'
    apply plugin: 'com.jfrog.bintray'

    sourceCompatibility = 1.7
    targetCompatibility = 1.7

    dependencies {
        testCompile 'junit:junit:4.7'
    }

    // custom tasks for creating source/javadoc jars
    task sourcesJar(type: Jar, dependsOn: classes) {
        classifier = 'sources'
        from sourceSets.main.allSource
    }

    task javadocJar(type: Jar, dependsOn: javadoc) {
        classifier = 'javadoc'
        from javadoc.destinationDir
    }

    // add javadoc/source jar tasks as artifacts
    artifacts {
        archives sourcesJar, javadocJar
    }

    repositories {
        jcenter()
    }

    publishing {
        publications {
            mavenJava(MavenPublication) {
                if (plugins.hasPlugin('war')) {
                    from components.web
                } else {
                    from components.java
                }

                artifact sourcesJar
                artifact javadocJar
            }
        }
    }

    bintray {
        user = bintrayUser // from gradle.properties file in ~/.gradle
        key  = bintrayKey // from gradle.properties file in ~/.gradle

        publications = ['mavenJava'] // When uploading Maven-based publication files
        dryRun = false // Whether to run this as dry-run, without deploying
        publish = true // If version should be auto published after an upload
        pkg {
            repo = 'Java-WebSocket'
            userOrg = 'micronautics' // An optional organization name when the repo belongs to one of the user's orgs
            name = 'Java-WebSocket'
            desc = 'Publishing Java-WebSocket HEAD because that project seems abandoned'
            websiteUrl = 'https://github.com/TooTallNate/Java-WebSocket'
            issueTrackerUrl = 'https://github.com/TooTallNate/Java-WebSocket/issues'
                    vcsUrl = 'https://github.com/TooTallNate/Java-WebSocket.git'
            licenses = ['MIT']
            labels = ['WebSocket', 'Java']
            publicDownloadNumbers = true
            //attributes= ['a': ['ay1', 'ay2'], 'b': ['bee'], c: 'cee'] //Optional package-level attributes
            version {
                name = project.version //Bintray logical version name
                desc = 'Tagged HEAD'
                vcsTag = project.version
//                released  = 'optional, date of the version release' //2 possible values: date in the format of 'yyyy-MM-dd'T'HH:mm:ss.SSSZZ' OR a java.util.Date instance
//                attributes = ['gradle-plugin': 'com.use.less:com.use.less.gradle:gradle-useless-plugin'] //Optional version-level attributes
//                gpg {
//                    sign = true //Determines whether to GPG sign the files. The default is false
//                    passphrase = 'passphrase' //Optional. The passphrase for GPG signing'
//                }
                //mavenCentralSync {
                //    sync = false //Optional (true by default). Determines whether to sync the version to Maven Central.
                //    user = 'userToken' //OSS user token
                //    password = 'paasword' //OSS user password
                //    close = '1' //Optional property. By default the staging repository is closed and artifacts are released to Maven Central. You can optionally turn this behaviour off (by puting 0 as value) and release the version manually.
                //}
            }
        }
    }
}

task wrapper(type: Wrapper) {
    gradleVersion = '2.2.1'
}

output

$ gradle bintrayUpload

FAILURE: Build failed with an exception.

* What went wrong:
Task 'bintrayUpload' not found in root project 'Java-WebSocket'.

* Try:
Run gradle tasks to get a list of available tasks. Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 3.107 secs

Do you have a multi module build?
Why do you apply the plugins to subprojects?