github.com/MetalBlockchain/subnet-evm@v0.4.9/rpc/doc.go (about) 1 // (c) 2019-2020, Ava Labs, Inc. 2 // 3 // This file is a derived work, based on the go-ethereum library whose original 4 // notices appear below. 5 // 6 // It is distributed under a license compatible with the licensing terms of the 7 // original code from which it is derived. 8 // 9 // Much love to the original authors for their work. 10 // ********** 11 // Copyright 2015 The go-ethereum Authors 12 // This file is part of the go-ethereum library. 13 // 14 // The go-ethereum library is free software: you can redistribute it and/or modify 15 // it under the terms of the GNU Lesser General Public License as published by 16 // the Free Software Foundation, either version 3 of the License, or 17 // (at your option) any later version. 18 // 19 // The go-ethereum library is distributed in the hope that it will be useful, 20 // but WITHOUT ANY WARRANTY; without even the implied warranty of 21 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 22 // GNU Lesser General Public License for more details. 23 // 24 // You should have received a copy of the GNU Lesser General Public License 25 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. 26 27 /* 28 29 Package rpc implements bi-directional JSON-RPC 2.0 on multiple transports. 30 31 It provides access to the exported methods of an object across a network or other I/O 32 connection. After creating a server or client instance, objects can be registered to make 33 them visible as 'services'. Exported methods that follow specific conventions can be 34 called remotely. It also has support for the publish/subscribe pattern. 35 36 RPC Methods 37 38 Methods that satisfy the following criteria are made available for remote access: 39 40 - method must be exported 41 - method returns 0, 1 (response or error) or 2 (response and error) values 42 43 An example method: 44 45 func (s *CalcService) Add(a, b int) (int, error) 46 47 When the returned error isn't nil the returned integer is ignored and the error is sent 48 back to the client. Otherwise the returned integer is sent back to the client. 49 50 Optional arguments are supported by accepting pointer values as arguments. E.g. if we want 51 to do the addition in an optional finite field we can accept a mod argument as pointer 52 value. 53 54 func (s *CalcService) Add(a, b int, mod *int) (int, error) 55 56 This RPC method can be called with 2 integers and a null value as third argument. In that 57 case the mod argument will be nil. Or it can be called with 3 integers, in that case mod 58 will be pointing to the given third argument. Since the optional argument is the last 59 argument the RPC package will also accept 2 integers as arguments. It will pass the mod 60 argument as nil to the RPC method. 61 62 The server offers the ServeCodec method which accepts a ServerCodec instance. It will read 63 requests from the codec, process the request and sends the response back to the client 64 using the codec. The server can execute requests concurrently. Responses can be sent back 65 to the client out of order. 66 67 An example server which uses the JSON codec: 68 69 type CalculatorService struct {} 70 71 func (s *CalculatorService) Add(a, b int) int { 72 return a + b 73 } 74 75 func (s *CalculatorService) Div(a, b int) (int, error) { 76 if b == 0 { 77 return 0, errors.New("divide by zero") 78 } 79 return a/b, nil 80 } 81 82 calculator := new(CalculatorService) 83 server := NewServer() 84 server.RegisterName("calculator", calculator) 85 l, _ := net.ListenUnix("unix", &net.UnixAddr{Net: "unix", Name: "/tmp/calculator.sock"}) 86 server.ServeListener(l) 87 88 Subscriptions 89 90 The package also supports the publish subscribe pattern through the use of subscriptions. 91 A method that is considered eligible for notifications must satisfy the following 92 criteria: 93 94 - method must be exported 95 - first method argument type must be context.Context 96 - method must have return types (rpc.Subscription, error) 97 98 An example method: 99 100 func (s *BlockChainService) NewBlocks(ctx context.Context) (rpc.Subscription, error) { 101 ... 102 } 103 104 When the service containing the subscription method is registered to the server, for 105 example under the "blockchain" namespace, a subscription is created by calling the 106 "blockchain_subscribe" method. 107 108 Subscriptions are deleted when the user sends an unsubscribe request or when the 109 connection which was used to create the subscription is closed. This can be initiated by 110 the client and server. The server will close the connection for any write error. 111 112 For more information about subscriptions, see https://github.com/ethereum/go-ethereum/wiki/RPC-PUB-SUB. 113 114 Reverse Calls 115 116 In any method handler, an instance of rpc.Client can be accessed through the 117 ClientFromContext method. Using this client instance, server-to-client method calls can be 118 performed on the RPC connection. 119 */ 120 package rpc