@modelcontextprotocol/sdk
Version:
Model Context Protocol implementation for TypeScript
95 lines • 3.69 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
/**
* SSE Polling Example Client (SEP-1699)
*
* This example demonstrates client-side behavior during server-initiated
* SSE stream disconnection and automatic reconnection.
*
* Key features demonstrated:
* - Automatic reconnection when server closes SSE stream
* - Event replay via Last-Event-ID header
* - Resumption token tracking via onresumptiontoken callback
*
* Run with: npx tsx src/examples/client/ssePollingClient.ts
* Requires: ssePollingExample.ts server running on port 3001
*/
const index_js_1 = require("../../client/index.js");
const streamableHttp_js_1 = require("../../client/streamableHttp.js");
const types_js_1 = require("../../types.js");
const SERVER_URL = 'http://localhost:3001/mcp';
async function main() {
console.log('SSE Polling Example Client');
console.log('==========================');
console.log(`Connecting to ${SERVER_URL}...`);
console.log('');
// Create transport with reconnection options
const transport = new streamableHttp_js_1.StreamableHTTPClientTransport(new URL(SERVER_URL), {
// Use default reconnection options - SDK handles automatic reconnection
});
// Track the last event ID for debugging
let lastEventId;
// Set up transport error handler to observe disconnections
// Filter out expected errors from SSE reconnection
transport.onerror = error => {
// Skip abort errors during intentional close
if (error.message.includes('AbortError'))
return;
// Show SSE disconnect (expected when server closes stream)
if (error.message.includes('Unexpected end of JSON')) {
console.log('[Transport] SSE stream disconnected - client will auto-reconnect');
return;
}
console.log(`[Transport] Error: ${error.message}`);
};
// Set up transport close handler
transport.onclose = () => {
console.log('[Transport] Connection closed');
};
// Create and connect client
const client = new index_js_1.Client({
name: 'sse-polling-client',
version: '1.0.0'
});
// Set up notification handler to receive progress updates
client.setNotificationHandler(types_js_1.LoggingMessageNotificationSchema, notification => {
const data = notification.params.data;
console.log(`[Notification] ${data}`);
});
try {
await client.connect(transport);
console.log('[Client] Connected successfully');
console.log('');
// Call the long-task tool
console.log('[Client] Calling long-task tool...');
console.log('[Client] Server will disconnect mid-task to demonstrate polling');
console.log('');
const result = await client.request({
method: 'tools/call',
params: {
name: 'long-task',
arguments: {}
}
}, types_js_1.CallToolResultSchema, {
// Track resumption tokens for debugging
onresumptiontoken: token => {
lastEventId = token;
console.log(`[Event ID] ${token}`);
}
});
console.log('');
console.log('[Client] Tool completed!');
console.log(`[Result] ${JSON.stringify(result.content, null, 2)}`);
console.log('');
console.log(`[Debug] Final event ID: ${lastEventId}`);
}
catch (error) {
console.error('[Error]', error);
}
finally {
await transport.close();
console.log('[Client] Disconnected');
}
}
main().catch(console.error);
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