MCP Dev Server Manager

A daemon that accepts requests from MCP clients to start dev servers, allocating unique ports to avoid collisions and shutting down idle connections after 120s of inactivity.

Example

• User starts daemon
• User’s first MCP client (eg coding CLI) requests to run a dev server
  • Dev server is started on PORT 3010
• User’s second MCP client (eg coding CLI) requests to run a dev server
  • Dev server is started on PORT 3011

Features

• Run multiple dev servers in parallel: useful if you want to use automated testing tools eg Playwright or Google Dev Tools MCP
• Avoid port collisions: when working with websites, it’s often necessary to specify different ports if you want to run multiple dev servers
• Automatic port allocation starting at 3010 with reuse
• Log capture with 512KB ring buffers per server
• Auto-cleanup of idle sessions after 120 seconds (configurable via --idle-timeout)

Installation & Usage

Requirements: Node.js >= 18

The recommended way to use dev-manager-mcp is via npx:

Quick Start

Make sure the daemon is running in a terminal somewhere:

npx -y dev-manager-mcp

Add this MCP config to your coding CLI:

{
  "mcpServers": {
    "dev-manager": {
      "command": "npx",
      "args": ["dev-manager-mcp", "stdio"]
    }
  }
}

Finally, ask your coding CLI to start a dev server. You should see it use the MCP server.

MCP Tools

start

Start a development server. Auto-generates a unique 4-character session key.

Parameters:

• command (string): Shell command to execute (e.g., “npm run dev”, “python -m http.server 8080”)
• cwd (optional string): Working directory for the command. When using STDIO transport, defaults to client’s working directory.

Returns:

{
  "status": "started",
  "port": 3010,
  "session_key": "A3X9"
}

stop

Stop a running development server session.

Parameters:

• session_key (string): Session identifier

Returns:

{
  "status": "stopped",
  "session_key": "A3X9"
}

status

Get status of one or all development server sessions.

Parameters:

• session_key (optional string): Specific session to query, or omit for all sessions

Returns:

{
  "sessions": [
    {
      "session_key": "B7K2",
      "port": 3010,
      "running": true
    }
  ]
}

tail

Get stdout/stderr logs for a development server session.

Parameters:

• session_key (string): Session identifier (e.g., “A3X9”)

Returns:

{
  "session_key": "A3X9",
  "stdout": "Server started on port 3010...",
  "stderr": ""
}

Architecture

Modules

• port_allocator.rs - Sequential port allocation from 3010 with free list
• log_buffer.rs - Bounded 512KB ring buffer with Clone support
• server_entry.rs - Process wrapper with async log capture
• manager.rs - Shared state manager with auto-cleanup sweeper
• service.rs - MCP service with tool definitions
• main.rs - HTTP/SSE daemon server

State Management

• Single Arc shared across all client connections
• Each connection gets a fresh DevManagerService instance
• Mutex-protected HashMap for session storage
• Background sweeper runs every 5 seconds to clean up idle sessions (>120s by default)

Session Keys

• Auto-generated 4-character uppercase alphanumeric codes (e.g., “A3X9”, “K7M2”)
• Guaranteed unique across active sessions
• 1,679,616 possible combinations (36^4)

Port Allocation

• Starts at 3010 and increments sequentially
• Maintains free list for reused ports
• Probes availability with TcpListener before assignment

Log Capture

• Each server spawns two async tasks for stdout/stderr
• Logs stored in bounded VecDeque with byte tracking
• Oldest entries evicted when 512KB limit reached
• Non-blocking reads with line buffering

Testing Multi-Client Behavior

1. Start daemon: npx -y dev-manager-mcp daemon
2. Connect Client A and start a server session
3. Connect Client B and query status - should see Client A’s session
4. Client B can stop Client A’s session
5. All clients share the same session state

Building from Source

If you prefer to build from source or need offline/advanced usage:

cargo build --release

The binary will be at target/release/dev-manager-mcp.

To use the built binary, replace npx dev-manager-mcp with ./target/release/dev-manager-mcp in all examples above.

License

MIT