Transport
The communication layer that handles message exchange between MCP clients and servers, supporting stdio and HTTP protocols with JSON-RPC formatting.
Transport
The transport layer handles the actual communication between MCP clients and servers. All transports use JSON-RPC 2.0 to exchange messages, providing a standardized way to connect different applications regardless of their implementation language.
Transport Types
| Transport | Use Case | Characteristics |
|---|---|---|
| Stdio | Local processes | Uses standard input/output, ideal for same-machine communication |
| HTTP | Remote connections | Uses HTTP POST with optional Server-Sent Events for streaming |
Message Format
All transports use JSON-RPC 2.0 with four message types:
// Request (expects response)
{
"jsonrpc": "2.0",
"method": "tools/list",
"id": 1
}
// Result (successful response)
{
"jsonrpc": "2.0",
"result": { "tools": [...] },
"id": 1
}
// Error (failed response)
{
"jsonrpc": "2.0",
"error": {
"code": -32601,
"message": "Method not found"
},
"id": 1
}
// Notification (one-way message)
{
"jsonrpc": "2.0",
"method": "notifications/initialized"
}
Connection Lifecycle
- Initialization - Client sends
initializerequest - Capability Exchange - Server responds with supported features
- Acknowledgment - Client sends
initializednotification - Message Exchange - Normal request/response flow begins
- Termination - Clean shutdown or error conditions
Transport Selection
- Local Communication - Use stdio for efficiency and simple process management
- Remote Communication - Use HTTP for network compatibility and security features
Related Terms
- MCP Client
- MCP Server
- Host