karatelabs/karate · error · RuntimeException

waitForPort() needs host and port arguments

Error message

waitForPort() needs host and port arguments

What it means

Arity guard in karate.waitForPort(): both a host and a port are required to attempt the TCP connection poll. Fires when fewer than two arguments are given; pass host and port (optional timeout/poll interval may follow).

Solutions

1. Supply both arguments: karate.waitForPort('localhost', 8080)
2. Pass the port as a number (other types are converted but a Number is cleanest)
3. Check the call site passes variables that are both defined

Example fix

// before
karate.waitForPort(host);
// after
karate.waitForPort(host, 9092);

// JS
if (host == null || port == null) throw new Error('waitForPort needs host and port');
karate.waitForPort(host, port);

// JS
function canWaitForPort(h, p) { return typeof h === 'string' && h.length > 0 && typeof p === 'number'; }

if (arguments.length < 2) throw new Error('usage: karate.waitForPort(host, port)');

When it happens

Trigger: Invoking karate.waitForPort('localhost') or karate.waitForPort() — any call supplying fewer than two arguments.

Common situations: Omitting the port when it was assumed to default (it does not); partial refactor of a call site; confusing this API with a single-object-argument style.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• waitForHttp() needs a URL argument
• eval() needs one argument
• expect() needs at least one argument
• remove() needs two arguments: variable name and path
• setXml() needs at least two arguments: name and xml

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/7488da8efc49f989. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/core/KarateJsUtils.java:1110

                try {
                    Thread.sleep(pollMs);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    return false;
                }
            }
            throw new RuntimeException("HTTP endpoint not available: " + url);
        };
    }

    /**
     * karate.waitForPort(host, port) - Wait for a TCP port to become available.
     * Polls until a TCP connection can be established.
     */
    static JavaInvokable waitForPort() {
        return args -> {
            if (args.length < 2) {
                throw new RuntimeException("waitForPort() needs host and port arguments");
            }
            String host = args[0] + "";
            int port;
            if (args[1] instanceof Number) {
                port = ((Number) args[1]).intValue();
            } else {
                port = Integer.parseInt(args[1].toString());
            }
            int timeoutMs = 30000;
            int pollMs = 250;
            if (args.length > 2 && args[2] instanceof Number) {
                timeoutMs = ((Number) args[2]).intValue();
            }
            if (args.length > 3 && args[3] instanceof Number) {
                pollMs = ((Number) args[3]).intValue();
            }
            long deadline = System.currentTimeMillis() + timeoutMs;
            while (System.currentTimeMillis() < deadline) {

View on GitHub (pinned to a22eb90246)