SIP Inspector (often referred to in its commercial branch as SIP Inspector Pro) is a lightweight, Java-based protocol simulation and testing tool designed specifically for Voice over IP (VoIP) and telephony engineers.
Created in 2008 by developer Žarko, it addresses the need for an easy-to-use tool to troubleshoot complex, “rainy day” signaling scenarios and conduct protocol analysis without the steep cost or complexity of enterprise software. Key Capabilities and Features
The application operates as a highly flexible SIP user agent and signaling simulator. Telephony engineers rely on it for several core functions:
Custom Scenario Creation: Users can design custom signaling scenarios using simple scripts or UI tools to mimic specific call flows (e.g., standard calls, transfers, holds, or custom error code handling).
Packet and Header Manipulation: Unlike strict commercial softphones, SIP Inspector allows engineers to manually manipulate headers, inject random variables (like varying the To and From fields), and test how SIP proxies or session border controllers (SBCs) handle malformed or unique syntax.
Media Emulation (RTP Streaming): It does not just simulate signaling; it can read raw media streams from existing Wireshark packet captures (.pcap) and play back the Real-time Transport Protocol (RTP) stream to verify audio paths.
Load and Automation Testing: The tool is efficient enough to run basic load tests, simulate multiple simultaneous dialogs, and automate repetitive protocol verification checks.
Transport Flexibility: It natively supports message transmission over both UDP and TCP transport layers. Core Engineering Use Cases
Telephony engineers primarily utilize the platform to isolate tricky network glitches:
Simulating Borderline Failures: Replicating rare protocol failures, unexpected timeouts, or 4xx/5xx/6xx response codes to ensure downstream softswitches fail gracefully.
Interoperability Testing: Verifying how two different vendor platforms communicate across a SIP trunk by sitting in the middle as an active probe.
One-Way Audio Diagnostics: Confirming firewalls or NAT boundaries are dropping audio packets by forcing specific RTP port binding variations. Licensing and Logistics
The software has evolved through several iterations (v3.xx through v6.xx). Home | SIPInspector Pro