C++

1. protocolbuffers/protobuf
   Protocol Buffers - Google's data interchange format
2. aria2/aria2
   aria2 is a lightweight multi-protocol & multi-source, cross platform download utility operated in command-line. It supports HTTP/HTTPS, FTP, SFTP, BitTorrent and Metalink.
3. google/flatbuffers
   FlatBuffers: Memory Efficient Serialization Library
4. apache/incubator-brpc
   Industrial-grade RPC framework used throughout Baidu, with 1,000,000+ instances and thousands kinds of services. "brpc" means "better RPC".
5. RPCS3/rpcs3
   PS3 emulator/debugger
6. TarsCloud/Tars
   Tars is a high-performance RPC framework based on name service and Tars protocol, also integrated administration platform, and implemented hosting-service via flexible schedule.
7. capnproto/capnproto
   Cap'n Proto serialization/RPC system - core tools and C++ library
8. idealvin/cocoyaxi
   A go-style coroutine library in C++11 and more.
9. baidu/sofa-pbrpc
   A light-weight RPC implement of google protobuf RPC framework.
10. zeroc-ice/ice
    Comprehensive RPC framework with support for C++, C#, Java, JavaScript, Python and more.
11. Tencent/phxrpc
    A simple C++ based RPC framework.
12. FISCO-BCOS/FISCO-BCOS
    FISCO BCOS 是由微众牵头的金链盟主导研发、对外开源、安全可控的企业级金融区块链底层技术平台。 单链配置下，性能 TPS 可达万级。提供群组架构、并行计算、分布式存储、可插拔的共识机制、隐私保护算法、支持全链路国密算法等诸多特性。 经过多个机构、多个应用，长时间在生产环境中的实践检验，具备金融级的高性能、高可用性及高安全性。FISCO BCOS is a secure and reliable financial-grade open-source blockchain platform. The platform provides rich features including group architecture, cross-chain communication protocols, pluggable consensus mechanisms, privacy protection algorithms, OSCCA-approved (Office of State Commercial Cryptography Administration) cryptography algorithms, and distributed storage. Its performance, usability, and security have been testified by many institutional users and successful business applications in a live production environment.
13. rpclib/rpclib
    rpclib is a modern C++ msgpack-RPC server and client library
14. sogou/srpc
    High performance, low latency, lightweight enterprise-level RPC system. Supports Baidu bRPC, Tencent tRPC, thrift protocols.

Go

1. asim/go-micro
   A Go microservices framework
2. chai2010/advanced-go-programming-book
   :books: 《Go 语言高级编程》开源图书，涵盖 CGO、Go 汇编语言、RPC 实现、Protobuf 插件实现、Web 框架实现、分布式系统等高阶主题(完稿)
3. zeromicro/go-zero
   A web and RPC framework written in Go. It's born to ensure the stability of the busy sites with resilient design. Builtin goctl greatly improves the development productivity.
4. grpc/grpc-go
   The Go language implementation of gRPC. HTTP/2 based RPC
5. geektutu/7days-golang
   7 days golang programs from scratch (web framework Gee, distributed cache GeeCache, object relational mapping ORM framework GeeORM, rpc framework GeeRPC etc) 7 天用 Go 动手写/从零实现系列
6. smallnest/rpcx
   Best microservices framework in Go, like alibaba Dubbo, but with more features, Scale easily. Try it. Test it. If you feel it's better, use it! 𝐉𝐚𝐯𝐚 有 𝐝𝐮𝐛𝐛𝐨, 𝐆𝐨𝐥𝐚𝐧𝐠 有 𝐫𝐩𝐜𝐱! build for clound!
7. roadrunner-server/roadrunner
   🤯 High-performance PHP application server, load-balancer and process manager written in Golang
8. twitchtv/twirp
   A simple RPC framework with protobuf service definitions
9. cloudwego/kitex
   A high-performance and strong-extensibility Golang RPC framework that helps developers build microservices.
10. davyxu/cellnet
    High performance, simple, extensible golang open source network library
11. hashicorp/go-plugin
    Golang plugin system over RPC.
12. TarsCloud/TarsGo
    A high performance microservice framework in golang. A linux foundation project.

Java

1. doocs/advanced-java
   😮 Core Interview Questions & Answers For Experienced Java(Backend) Developers | 互联网 Java 工程师进阶知识完全扫盲：涵盖高并发、分布式、高可用、微服务、海量数据处理等领域知识
2. apache/dubbo
   Apache Dubbo is a high-performance, java based, open source RPC framework.
3. redisson/redisson
   Redisson - Redis Java client with features of In-Memory Data Grid. Over 50 Redis based Java objects and services: Set, Multimap, SortedSet, Map, List, Queue, Deque, Semaphore, Lock, AtomicLong, Map Reduce, Publish / Subscribe, Bloom filter, Spring Cache, Tomcat, Scheduler, JCache API, Hibernate, MyBatis, RPC, local cache ...
4. dianping/cat
   CAT 作为服务端项目基础组件，提供了 Java, C/C++, Node.js, Python, Go 等多语言客户端，已经在美团点评的基础架构中间件框架（MVC 框架，RPC 框架，数据库框架，缓存框架等，消息队列，配置系统等）深度集成，为美团点评各业务线提供系统丰富的性能指标、健康状况、实时告警等。
5. grpc/grpc-java
   The Java gRPC implementation. HTTP/2 based RPC
6. nathanmarz/storm
   Distributed and fault-tolerant realtime computation: stream processing, continuous computation, distributed RPC, and more
7. weibocom/motan
   A cross-language remote procedure call(RPC) framework for rapid development of high performance distributed services.
8. line/armeria
   Your go-to microservice framework for any situation, from the creator of Netty et al. You can build any type of microservice leveraging your favorite technologies, including gRPC, Thrift, Kotlin, Retrofit, Reactive Streams, Spring Boot and Dropwizard.
9. sofastack/sofa-rpc
   SOFARPC is a high-performance, high-extensibility, production-level Java RPC framework.

Python

1. crossbario/autobahn-python
   WebSocket and WAMP in Python for Twisted and asyncio
2. quantmind/pulsar
   Event driven concurrent framework for Python
3. lgandx/PCredz
   This tool extracts Credit card numbers, NTLM(DCE-RPC, HTTP, SQL, LDAP, etc), Kerberos (AS-REQ Pre-Auth etype 23), HTTP Basic, SNMP, POP, SMTP, FTP, IMAP, etc from a pcap file or from a live interface.
4. Thriftpy/thriftpy
   Thriftpy has been deprecated, please migrate to https://github.com/Thriftpy/thriftpy2
5. tomerfiliba-org/rpyc
   RPyC (Remote Python Call) - A transparent and symmetric RPC library for python
6. samuelcolvin/arq
   Fast job queuing and RPC in python with asyncio and redis.
7. arskom/spyne
   A transport agnostic sync/async RPC library that focuses on exposing services with a well-defined API using popular protocols.
8. jgarzik/python-bitcoinrpc
   Python interface to bitcoin's JSON-RPC API
9. Pyrlang/Pyrlang
   Erlang node implemented in Python 3.5+ (Asyncio-based)
10. Thriftpy/thriftpy2
    Pure python approach of Apache Thrift.
11. kevinhwang91/rnvimr
    Make Ranger running in a floating window to communicate with Neovim via RPC
12. hakril/PythonForWindows
    A codebase aimed to make interaction with Windows and native execution easier
13. joshmarshall/jsonrpclib
    A Python JSON-RPC over HTTP that mirrors xmlrpclib syntax.
14. CiscoDevNet/yang-explorer
    An open-source Yang Browser and RPC Builder Application
15. phunt/avro-rpc-quickstart
    Apache Avro RPC Quick Start.
16. pavlov99/json-rpc
    🔁 JSON-RPC 1/2 transport implementation. Supports python 2/3 and pypy.
17. progrium/duplex
    Full duplex modern RPC
18. maxcutler/python-wordpress-xmlrpc
    Python library for WordPress XML-RPC integration
19. studio-ousia/mprpc
    A fast Python RPC library
20. Ananto30/zero
    Zero: A simple, fast, high performance and low latency Python framework (RPC + PubSub) for building microservices or distributed servers