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Host vs Client vs Server

🔌 Foundation⏱ 6 min⭐ 50 BASE XP

Distinguishing the Roles

Understanding the difference between the Host, Client, and Server is critical when debugging MCP setups.

ComponentRoleExamples
HostUser interface and LLM communication. Manages multiple clients.Claude Desktop, VS Code, Cursor
ClientProtocol-level state machine. Sends requests, parses responses.@modelcontextprotocol/sdk/client
ServerExecutes code, talks to databases/APIs, provides data.mcp-server-postgres, mcp-github
💡 Key Insight: There is a strict 1-to-1 relationship between an MCP Client instance and an MCP Server. The Host application usually runs many Client instances to talk to multiple Servers simultaneously.
SYNAPSE VERIFICATION
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What is the relationship between MCP Clients and MCP Servers?
Many-to-Many
One-to-Many (One client, many servers)
One-to-One
Many-to-One
Watch: 139x Rust Speedup
Host vs Client vs Server | Foundation — MCP Academy