直接从 Golang 打印到外部打印机

是的！下面使用 IPP（互联网打印协议）从 Golang 打印 postscript 文件，过去 20 年制造的大多数网络打印机都支持该协议：

import (

    "bytes"

    "fmt"

    "io"

    "io/ioutil"

    "net/http"

    "os"

    "strconv"

    "github.com/alexflint/go-arg"

    "github.com/kr/pretty"

    "github.com/phin1x/go-ipp"

)

func Main() error {

    var args struct {

        URI            string `arg:"positional,required"`

        PostscriptFile string `arg:"positional,required"`

    }

    arg.MustParse(&args)

    // define a ipp request

    req := ipp.NewRequest(ipp.OperationPrintJob, 1)

    req.OperationAttributes[ipp.AttributeCharset] = "utf-8"

    req.OperationAttributes[ipp.AttributeNaturalLanguage] = "en"

    req.OperationAttributes[ipp.AttributePrinterURI] = args.URI

    req.OperationAttributes[ipp.AttributeRequestingUserName] = "some-user"

    req.OperationAttributes[ipp.AttributeDocumentFormat] = "application/octet-stream"

    // encode request to bytes

    payload, err := req.Encode()

    if err != nil {

        return fmt.Errorf("error encoding ipp request: %w", err)

    }

    // read the test page

    postscript, err := ioutil.ReadFile(args.PostscriptFile)

    if err != nil {

        return fmt.Errorf("error reading postscript file: %w", err)

    }

    payload = append(payload, postscript...)

    // send ipp request to remote server via http

    httpReq, err := http.NewRequest("POST", args.URI, bytes.NewReader(payload))

    if err != nil {

        return fmt.Errorf("error creating http request: %w", err)

    }

    // set ipp headers

    httpReq.Header.Set("Content-Length", strconv.Itoa(len(payload)))

    httpReq.Header.Set("Content-Type", ipp.ContentTypeIPP)

    // perform the request

    var httpClient http.Client

    httpResp, err := httpClient.Do(httpReq)

    if err != nil {

        return fmt.Errorf("error executing http request: %w", err)

    }

    defer httpResp.Body.Close()

    // read the response

    buf, err := io.ReadAll(httpResp.Body)

    if err != nil {

        return fmt.Errorf("error reading response body: %w", err)

    }

    // response must be 200 for a successful operation

    // other possible http codes are:

    // - 500 -> server error

    // - 426 -> sever requests a encrypted connection

    // - 401 -> forbidden -> need authorization header or user is not permitted

    if httpResp.StatusCode != 200 {

        return fmt.Errorf("printer said %d: %s", httpResp.StatusCode, buf)

    }

    // decode ipp response

    resp, err := ipp.NewResponseDecoder(bytes.NewReader(buf)).Decode(nil)

    if err != nil {

        return fmt.Errorf("error decoding ipp response: %w", err)

    }

    // print the response

    fmt.Println("Submitted print job. Response was:")

    pretty.Println(resp)

    return nil

}

使用的 URL 只是 http://ip-address-of-myprinter（这是在兄弟 HL 系列打印机上测试的）