如何使用编码器/解码器发送/接收Go Unix Socket JSON字符串[重复]

Question

This question already has an answer here:

• Unable to unmarshal JSON into struct 1 answer

We are building a trivial cache process which runs on every node. Each has multiple services up and running and tries to connect to this local cache process which receives the JSON string as an input, and sends the required details in JSON format.

As of now, we have tried the below approach and it seems the local socket communication with encoder, decoder is giving empty results.

Server Code

package main

import (
    "encoding/json"
    "fmt"
    "net"
    "os"
)

var sockLocArg = "/tmp/.testsock"

type sockOut struct {
    keyCheckSum   uint32 `json:"keyCheckSum"`
    valueCheckSum uint32 `json:"valueCheckSum"`
    emsg          string `json:"emsg"`
}

type sockIn struct {
    action   string `json:"action"`
    compName string `json:"compname"`
}

func processSockRequest(c net.Conn) {

    defer c.Close()
    decode := json.NewDecoder(c)
    encode := json.NewEncoder(c)

    var inputJSON sockIn
    err := decode.Decode(&inputJSON)
    if err != nil {
        fmt.Printf("Error is %v", err)
    }
    fmt.Printf("Action: %s, CompName: %s
", inputJSON.action, inputJSON.compName)

    outputJSON := sockOut{
        keyCheckSum:   10,
        valueCheckSum: 10,
        emsg:          "",
    }
    // Send response back to the socket request
    err = encode.Encode(outputJSON)
    if err != nil {
        fmt.Printf("Error is %v", err)
    }
}

func initSocket() {
    // Creating the unix domain TCP socket
    //
    localSocket, err := net.Listen("unix", sockLocArg)
    if err != nil {
        fmt.Printf("Unable to create unix domain socket. Error: %v", err)
        os.Exit(1)
    }
    // Set the permissions 700 on this
    //
    if err = os.Chmod(sockLocArg, 0700); err != nil {
        fmt.Printf("Unable to change the permissions for the socket. Error: %v", err)
        os.Exit(1)
    }
    // Initiate and listen to the socket
    //
    for {
        SockFileDescriptor, err := localSocket.Accept()
        if err != nil {
            fmt.Printf("Unable to accept incoming messages over the socket. Error: %v", err)
            os.Exit(1)
        }
        processSockRequest(SockFileDescriptor)
    }
}

func main() {
    initSocket()
}

Client Code

package main

import (
    "encoding/json"
    "fmt"
    "net"
)

type sockOut struct {
    keyCheckSum   uint32 `json:"keyCheckSum"`
    valueCheckSum uint32 `json:"valueCheckSum"`
    emsg          string `json:"emsg"`
}

type sockIn struct {
    action   string `json:"action"`
    compName string `json:"compname"`
}

func main() {
    c, err := net.Dial("unix", "/tmp/.testsock")
    if err != nil {
        panic(err)
    }
    defer c.Close()

    //go reader(c)

    decode := json.NewDecoder(c)
    encode := json.NewEncoder(c)

    inputJSON := sockIn{
        action:   "GET",
        compName: "TEST",
    }
    err = encode.Encode(inputJSON)

    if err != nil {
        fmt.Printf("Error is: %v", err)
    }
    var outputJSON sockOut
    err = decode.Decode(&outputJSON)

    if err != nil {
        fmt.Printf("Error is %v", err)
    }
    fmt.Printf("KeyCheckSum: %d, ValueCheckSum: %d Error: %s
", outputJSON.keyCheckSum, outputJSON.valueCheckSum, outputJSON.emsg)
}

Output

Starting Server

bin/serv &
[1] 6195

Running Client

$ bin/client 
Action: , CompName: 
KeyCheckSum: 0, ValueCheckSum: 0 Error: 

Would someone provide some guidance on why we are getting this empty string between server and client communication. We are using Go version go1.8 darwin/amd64.

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Answer 1

JSON marshalling / unmarshalling only takes into account the public fields in a struct; i.e., their name must start with an uppercase letter.