gronod
49bc0775de
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Network MCP clients (e.g. browser-based frontends) can't spawn stdio subprocesses, so the server now optionally serves the 2024-11-05 MCP HTTP/SSE transport via MCP_TRANSPORT=sse and MCP_PORT (default 8080), backed by the SDK's SSEHandler behind permissive CORS. stdio remains the default and is behaviourally unchanged.
79 lines
2.4 KiB
Go
79 lines
2.4 KiB
Go
// Package transport wires the MCP server onto network transports.
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// The stdio transport is driven directly from the entrypoint; this
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// package owns the HTTP/SSE transport defined by the 2024-11-05 MCP
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// specification.
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package transport
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import (
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"context"
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"errors"
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"fmt"
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"net"
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"net/http"
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"time"
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"github.com/modelcontextprotocol/go-sdk/mcp"
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)
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// NewSSEHandler builds an http.Handler serving MCP over HTTP/SSE:
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//
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// GET /sse opens a session and streams server->client messages
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// as SSE events; the first event is an 'endpoint' event
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// carrying the session's POST URL (?sessionid=...).
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// POST /sse or /messages?sessionid=... accepts client->server JSON-RPC
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// messages for an established session.
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//
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// A permissive CORS middleware wraps the mux because network MCP servers
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// are frequently queried by browser-based clients.
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func NewSSEHandler(srv *mcp.Server) http.Handler {
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mcpHandler := mcp.NewSSEHandler(func(*http.Request) *mcp.Server { return srv }, nil)
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mux := http.NewServeMux()
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mux.Handle("/sse", mcpHandler)
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mux.Handle("/messages", mcpHandler)
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return cors(mux)
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}
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func cors(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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h := w.Header()
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h.Set("Access-Control-Allow-Origin", "*")
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h.Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
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h.Set("Access-Control-Allow-Headers", "Content-Type, Accept, Authorization")
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if r.Method == http.MethodOptions {
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w.WriteHeader(http.StatusNoContent)
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return
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}
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next.ServeHTTP(w, r)
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})
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}
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// RunSSE serves the MCP SSE transport on the given port until ctx is
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// cancelled, then shuts down gracefully.
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func RunSSE(ctx context.Context, srv *mcp.Server, port int) error {
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httpSrv := &http.Server{
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Addr: fmt.Sprintf(":%d", port),
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Handler: NewSSEHandler(srv),
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ReadHeaderTimeout: 10 * time.Second,
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}
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lc := net.ListenConfig{}
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ln, err := lc.Listen(ctx, "tcp", httpSrv.Addr)
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if err != nil {
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return fmt.Errorf("listen %s: %w", httpSrv.Addr, err)
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}
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errCh := make(chan error, 1)
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go func() {
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errCh <- httpSrv.Serve(ln)
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}()
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select {
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case <-ctx.Done():
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shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
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defer cancel()
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return httpSrv.Shutdown(shutdownCtx)
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case err := <-errCh:
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if errors.Is(err, http.ErrServerClosed) {
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return nil
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}
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return err
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}
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}
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