Software Engineer

Overview

C# Software Engineer, Remote, 12 month contract, Inside IR35. Must be eligible for BPSS clearance. Working one day a month on site in Rugby. Real-time system experience is essential for this role, working within an Agile delivery team, you will move beyond standard CRUD applications to solve complex network and real-time communication challenges. You will lead the development of expansion products that interface with 3GPP-compliant User Equipment (UE).

Responsibilities

• SIP Signaling & Session Management: Develop C# components for high-concurrency SIP sessions, managing complex headers and MIME bodies to support features like "First-to-Answer" and Group Regroups.
• Real-Time Media Plane: Implement RTP/RTCP media handling for Mission Critical Voice (MCPTT) and Video (MCVideo), ensuring seamless floor control (transmission rights) in half-duplex environments.
• Data & Configuration: Build handlers for MCData services (SDS, File Distribution) using HTTP and SIP MESSAGE requests, and manage XCAP retrieval logic for XML configuration documents.
• Secure Communications: Integrate OIDC authentication flows and MIKEY-SAKKE encryption to ensure media transport remains secure and resilient.

Essentials skills

• C# / .NET Framework / .NET Core Mastery: 3+ years of professional experience with a deep focus on asynchronous network programming.
• .NET Frameworks Experience: WCF, SignalR, EF, ASP.NET, WebAPI
• Protocol Expertise: A solid understanding of the SIP Protocol Stack (INVITE, PUBLISH, SUBSCRIBE, etc.) and experience with RTP/RTCP stacks.
• Data Handling: Proficiency in parsing complex XML schemas (XSD) and handling multipart/mixed MIME bodies.
• Software Engineering Principles: Strong grasp of OOP, SOLID principles, and modern CI/CD workflows (Git, Pull Requests, Agile).

Preferred skills

• 3GPP Standards: Familiarity with TS 24.379 (MCPTT) or related MCX standards.
• Security: Experience with SRTP, TLS, or Key Management lifecycles (KMS).
• Domain Knowledge: Previous experience with UK Police Control Room environments or the Emergency Services Network (ESN).

SmartSourcing are a Disability Confident Employer and we promote, celebrate and value diversity, we are committed to promoting equality and inclusion for all