直接从 Golang 打印到外部打印机

Golang 提供了一种直接从代码打印到物理外部打印机的方法，无需使用打印机驱动程序或复杂的系统设置。利用互联网打印协议 (IPP)，开发者可以发送打印作业请求，指定打印机 URI、文档格式和打印数据。该方法支持大多数网络打印机，无需额外的配置或依赖项。本文提供了一个代码示例，展示如何从 Golang 打印 PostScript 文件，只需提供打印机 URI 和 PostScript 文件路径即可。该代码通过 HTTP 向打印机发送 IPP 请求，打印机返回响应，指示打印作业状态。

我可以直接从 Golang 打印到我的（物理、外部）打印机，而不使用打印机驱动程序或 CUPS 或任何其他此类复杂性吗？

正确答案

是的！以下代码使用 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
}

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

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