MockaSIP - SIP Error Response Simulator

Quick Start

Get a SIP error response in three steps.

Pick an error code

Choose any SIP error code between 300 and 699.

Send an INVITE

Dial a SIP URI ending with that code, e.g. sip:test486@mockasip.com.

Get the response

MockaSIP replies with the matching SIP error and reason phrase.

Features

Everything you need for SIP error testing, nothing you don't.

Error Codes Only

Responds to codes 300-699: redirect, client error, server error, and global failure responses.

RFC Compliant

Proper SIP reason phrases based on RFC 3261 and related standards.

Simple Interface

No authentication or complex setup required for testing.

Automatic Extraction

Extracts the last 3 digits from any SIP INVITE user to determine the error code.

Rate Limited

Rate limited to 1 request per second per source IP to ensure fair usage for all testers.

Behavior

How MockaSIP interprets your request.

Condition	Response
Valid error code (300-699)	Returns the requested error code with the proper reason phrase
Non-error code (100-299)	`400 Bad Request - Invalid Status Code`
Code outside 100-699	`400 Bad Request - Invalid Status Code`
Username fewer than 3 characters	`400 Bad Request - User Part Too Short`
No INVITE username	`484 Address Incomplete`

Examples

Only the last 3 digits of the username matter. Use any prefix you like.

INVITE URI	Response
sip:404@mockasip.com	404 Not Found
sip:+353123486@mockasip.com	486 Busy Here
sip:anything503@mockasip.com	503 Service Unavailable

Tip: You can use any prefix (test, user, phone number, etc.) as long as the username ends with the desired 3-digit error code.

Rate Limit: The service is rate limited to 1 request per second per source IP. Requests exceeding this limit will be dropped.

Supported Error Codes

67 SIP error codes across all error categories.

300Multiple Choices

301Moved Permanently

302Moved Temporarily

305Use Proxy

380Alternative Service

Use Cases

Built for developers, testers, and anyone working with SIP.

SIP Client Development

Test how your client handles various error conditions without complex infrastructure.

SIP Trunk Testing

Test out SIP trunk failover scenarios.

Quality Assurance

Verify error handling behavior in automated tests and CI/CD pipelines.

Training & Learning

Learn about different SIP error codes and their meanings in a hands-on way.

Debugging

Reproduce specific error scenarios for troubleshooting and debugging.

FAQ

Common questions about using MockaSIP.

Why am I getting a 400 Bad Request?

This happens when the error code extracted from your username is outside the 300-699 range, or the username has fewer than 3 characters. Codes 100-299 are informational/success responses and are not supported as error simulations, so they also return 400 Bad Request - Invalid Status Code.

Does MockaSIP support TCP and TLS?

MockaSIP listens on UDP port 5060 by default. TCP and TLS are not currently supported.

Is authentication required?

No. MockaSIP is designed as an open testing tool. No registration or authentication is needed to use the service.

What if my desired code isn't in the supported list?

If you send a code in the 300-699 range that isn't explicitly listed, MockaSIP will return a 404 Not Found - Unsupported Status Code. Only the 67 codes listed above have standard RFC reason phrases.

Is there a rate limit?

Yes. The service is rate limited to 1 request per second per source IP address. Requests that exceed this limit will be dropped.

Can I use MockaSIP for automated testing?

Absolutely. MockaSIP is ideal for CI/CD pipelines and automated test suites. Just keep your test traffic within the rate limit of 1 request per second.