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Communication Protocols

Communication protocols are systems of rules that allow two or more entities in a networked system to exchange information. Modern API platforms rely on layered protocol stacks that span the physical and link layers, network and transport layers, and application protocols such as HTTP, gRPC, MQTT, AMQP, WebSockets, SSE, and Webhooks. The communication protocols topic surveys the most relevant standards bodies (IETF, W3C, IEEE, ITU, ISO), the most widely deployed protocols at each layer, and the way protocol choice shapes API design, performance, security, and interoperability.

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APIsApplication ProtocolsCommunication ProtocolsInternetIETFNetworkingReal-TimeStandardsTransportWeb

APIs

Hypertext Transfer Protocol (HTTP)

The application layer protocol that powers the World Wide Web and the majority of REST and HTTP APIs. HTTP/1.1 is defined in RFC 9110-9114, HTTP/2 in RFC 9113, and HTTP/3 in RFC...

gRPC

A high-performance, contract-first RPC framework built on HTTP/2 with Protocol Buffers as the default IDL. gRPC supports unary, server streaming, client streaming, and bidirecti...

GraphQL

A query language and runtime for client-driven data APIs over HTTP and WebSockets. GraphQL exposes a single endpoint with a typed schema defining queries, mutations, and subscri...

WebSocket

A bidirectional, full-duplex communication protocol over a single TCP connection, defined in RFC 6455. WebSocket upgrades from HTTP and is widely used for chat, collaborative ed...

MQTT

A lightweight publish-subscribe messaging protocol designed for constrained devices and unreliable networks. MQTT is an OASIS standard and is widely used in IoT, automotive, and...

AMQP

The Advanced Message Queuing Protocol, an OASIS standard for interoperable, broker-mediated messaging. AMQP 1.0 defines a wire protocol with strong typing, links, sessions, and ...

Webhooks

An HTTP-based pattern for delivering event notifications from one service to another by performing an outbound HTTP POST to a URL registered by the consumer. Webhooks are not a ...

Server-Sent Events (SSE)

A simple, one-way, server-to-client streaming protocol defined as part of the HTML living standard. SSE runs over plain HTTP, supports automatic reconnection, and is widely used...

Resources

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Documentation
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Reference
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Resources
Resources

Sources

apis.yml Raw ↑ 
aid: communication-protocols
url: >-
  https://raw.githubusercontent.com/api-evangelist/communication-protocols/refs/heads/main/apis.yml
name: Communication Protocols
kind: topic
description: >-
  Communication protocols are systems of rules that allow two or more entities
  in a networked system to exchange information. Modern API platforms rely on
  layered protocol stacks that span the physical and link layers, network and
  transport layers, and application protocols such as HTTP, gRPC, MQTT, AMQP,
  WebSockets, SSE, and Webhooks. The communication protocols topic surveys
  the most relevant standards bodies (IETF, W3C, IEEE, ITU, ISO), the most
  widely deployed protocols at each layer, and the way protocol choice shapes
  API design, performance, security, and interoperability.
image: https://kinlane-productions.s3.amazonaws.com/apis-json/apis-json-logo.jpg
tags:
- APIs
- Application Protocols
- Communication Protocols
- Internet
- IETF
- Networking
- Real-Time
- Standards
- Transport
- Web
created: '2025-01-01'
modified: '2026-04-28'
specificationVersion: '0.19'
apis:
- aid: communication-protocols:http
  name: Hypertext Transfer Protocol (HTTP)
  description: >-
    The application layer protocol that powers the World Wide Web and the
    majority of REST and HTTP APIs. HTTP/1.1 is defined in RFC 9110-9114,
    HTTP/2 in RFC 9113, and HTTP/3 in RFC 9114, the latter running over
    QUIC. HTTP defines methods, status codes, headers, content negotiation,
    caching, and conditional requests that underpin modern web APIs.
  humanURL: https://httpwg.org/specs/
  baseURL: https://httpwg.org
  tags:
  - Application Protocol
  - HTTP
  - IETF
  - REST
  - Web
  properties:
  - type: Specification
    url: https://www.rfc-editor.org/rfc/rfc9110
  - type: Specification
    url: https://www.rfc-editor.org/rfc/rfc9112
  - type: Specification
    url: https://www.rfc-editor.org/rfc/rfc9113
  - type: Specification
    url: https://www.rfc-editor.org/rfc/rfc9114
  - type: Working Group
    url: https://datatracker.ietf.org/wg/httpbis/about/
  x-features:
  - Stateless request/response model
  - Methods, status codes, headers, content negotiation
  - HTTP/2 multiplexing and HPACK header compression
  - HTTP/3 over QUIC for low-latency, head-of-line-free transport
  - Strong caching semantics with conditional requests
  x-useCases:
  - REST and resource-oriented APIs
  - GraphQL and gRPC-Web transport
  - Webhook delivery
  - Browser-to-API communication
- aid: communication-protocols:grpc
  name: gRPC
  description: >-
    A high-performance, contract-first RPC framework built on HTTP/2 with
    Protocol Buffers as the default IDL. gRPC supports unary, server
    streaming, client streaming, and bidirectional streaming and is widely
    used for microservice-to-microservice communication and for
    polyglot APIs across cloud-native platforms.
  humanURL: https://grpc.io/
  baseURL: https://grpc.io
  tags:
  - CNCF
  - HTTP/2
  - Protocol Buffers
  - RPC
  - Streaming
  properties:
  - type: Documentation
    url: https://grpc.io/docs/
  - type: Specification
    url: https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
  - type: GitHubOrganization
    url: https://github.com/grpc
  x-features:
  - HTTP/2 multiplexed transport with Protobuf payloads
  - Four streaming modes (unary, server, client, bidi)
  - Polyglot code generation across 11+ languages
  - Pluggable authentication, deadlines, and interceptors
  x-useCases:
  - Internal microservice communication
  - Mobile-to-backend APIs with low latency
  - High-throughput streaming workloads
  - Polyglot service interfaces
- aid: communication-protocols:graphql
  name: GraphQL
  description: >-
    A query language and runtime for client-driven data APIs over HTTP and
    WebSockets. GraphQL exposes a single endpoint with a typed schema
    defining queries, mutations, and subscriptions, allowing clients to
    request precisely the data they need.
  humanURL: https://graphql.org/
  baseURL: https://graphql.org
  tags:
  - API
  - GraphQL
  - HTTP
  - Schema
  - Subscriptions
  properties:
  - type: Specification
    url: https://spec.graphql.org/
  - type: Documentation
    url: https://graphql.org/learn/
  - type: Reference
    url: https://github.com/graphql/graphql-spec
  - url: graphql/communication-protocols-graphql.md
    type: GraphQL
  x-features:
  - Strongly typed schema definition language (SDL)
  - Single endpoint with arbitrary query shapes
  - Subscriptions for real-time pushes over WebSocket
  - Introspection enabling tooling and codegen
  x-useCases:
  - Aggregating data from multiple backends
  - Tailored mobile and web client payloads
  - BFF (backend for frontend) APIs
  - Real-time dashboards via subscriptions
- aid: communication-protocols:websocket
  name: WebSocket
  description: >-
    A bidirectional, full-duplex communication protocol over a single TCP
    connection, defined in RFC 6455. WebSocket upgrades from HTTP and is
    widely used for chat, collaborative editing, live dashboards, and game
    servers.
  humanURL: https://www.rfc-editor.org/rfc/rfc6455
  baseURL: https://www.rfc-editor.org
  tags:
  - Bidirectional
  - IETF
  - Real-Time
  - Web
  - WebSocket
  properties:
  - type: Specification
    url: https://www.rfc-editor.org/rfc/rfc6455
  - type: Documentation
    url: https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API
  x-features:
  - HTTP upgrade handshake to TCP-level full-duplex frames
  - Text and binary frame types
  - Subprotocol negotiation (e.g. graphql-ws, mqtt)
  - Native support in browsers and most server runtimes
  x-useCases:
  - Real-time chat and collaboration
  - Live tickers and dashboards
  - GraphQL subscription transport
  - Multiplayer games and signaling
- aid: communication-protocols:mqtt
  name: MQTT
  description: >-
    A lightweight publish-subscribe messaging protocol designed for
    constrained devices and unreliable networks. MQTT is an OASIS standard
    and is widely used in IoT, automotive, and edge environments. MQTT 5
    adds user properties, reason codes, shared subscriptions, and other
    modern features.
  humanURL: https://mqtt.org/
  baseURL: https://mqtt.org
  tags:
  - IoT
  - Lightweight
  - OASIS
  - Pub/Sub
  properties:
  - type: Specification
    url: https://docs.oasis-open.org/mqtt/mqtt/v5.0/mqtt-v5.0.html
  - type: Documentation
    url: https://mqtt.org/getting-started/
  - type: Reference
    url: https://www.hivemq.com/mqtt/mqtt-essentials/
  x-features:
  - Tiny binary protocol with three QoS levels
  - Hierarchical topic-based pub/sub
  - Retained messages and last-will-and-testament
  - MQTT 5 reason codes, properties, and shared subscriptions
  x-useCases:
  - IoT telemetry and command/control
  - Automotive and industrial messaging
  - Mobile push and presence
  - Edge-to-cloud streaming
- aid: communication-protocols:amqp
  name: AMQP
  description: >-
    The Advanced Message Queuing Protocol, an OASIS standard for
    interoperable, broker-mediated messaging. AMQP 1.0 defines a wire
    protocol with strong typing, links, sessions, and connection-level
    security and is used by RabbitMQ, Azure Service Bus, and many other
    brokers.
  humanURL: https://www.amqp.org/
  baseURL: https://www.amqp.org
  tags:
  - Brokered
  - Enterprise Messaging
  - OASIS
  - Queuing
  properties:
  - type: Specification
    url: https://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-overview-v1.0-os.html
  - type: Documentation
    url: https://www.rabbitmq.com/protocol.html
  x-features:
  - Wire-level interoperability across brokers
  - Reliable, transactional messaging with sessions and links
  - SASL-based authentication and TLS transport
  x-useCases:
  - Enterprise integration and ESB scenarios
  - Cross-language work queues and task distribution
  - Cloud broker messaging on Azure Service Bus
- aid: communication-protocols:webhooks
  name: Webhooks
  description: >-
    An HTTP-based pattern for delivering event notifications from one
    service to another by performing an outbound HTTP POST to a URL
    registered by the consumer. Webhooks are not a single specification
    but the broader pattern is increasingly governed by efforts such as
    the CloudEvents specification and the IETF Webhook security drafts.
  humanURL: https://webhooks.fyi/
  baseURL: https://webhooks.fyi
  tags:
  - Async
  - Events
  - HTTP
  - Push
  properties:
  - type: Reference
    url: https://webhooks.fyi/
  - type: Specification
    url: https://cloudevents.io/
  - type: Documentation
    url: https://www.standardwebhooks.com/
  x-features:
  - Outbound HTTP POST event delivery
  - Pluggable signing schemes (HMAC, JWT) for verification
  - Replay protection with timestamps and nonces
  - Aligns with CloudEvents and Standard Webhooks
  x-useCases:
  - Asynchronous event delivery between SaaS platforms
  - Build, deploy, and CI pipeline notifications
  - Payment and billing event hooks
  - Third-party integrations without polling
- aid: communication-protocols:server-sent-events
  name: Server-Sent Events (SSE)
  description: >-
    A simple, one-way, server-to-client streaming protocol defined as part
    of the HTML living standard. SSE runs over plain HTTP, supports
    automatic reconnection, and is widely used for live status feeds and
    LLM token streaming.
  humanURL: https://html.spec.whatwg.org/multipage/server-sent-events.html
  baseURL: https://html.spec.whatwg.org
  tags:
  - HTML
  - HTTP
  - Real-Time
  - Streaming
  properties:
  - type: Specification
    url: https://html.spec.whatwg.org/multipage/server-sent-events.html
  - type: Documentation
    url: https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events
  x-features:
  - Plain HTTP text/event-stream responses
  - Automatic browser reconnection with Last-Event-ID
  - Simpler than WebSocket for one-way fan-out
  x-useCases:
  - LLM token streaming
  - Live status and activity feeds
  - Server-pushed dashboards
common:
- type: Documentation
  url: https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml
- type: Reference
  url: https://www.rfc-editor.org/standards
- type: Reference
  url: https://www.iso.org/standard/74534.html
- type: Reference
  url: https://en.wikipedia.org/wiki/Communication_protocol
- type: Resources
  url: https://www.cncf.io/
maintainers:
- FN: Kin Lane
  email: [email protected]