当我使用网络连接的 Epson WorkForce 435 打印机进行打印时，我在 /var/log/cups/error_log 中收到以下错误消息：
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Active clients", busy="Not busy"
D [29/Aug/2021:16:58:51 +1000] [Client 20] Server address is "/run/cups/cups.sock".
D [29/Aug/2021:16:58:51 +1000] [Client 20] Accepted from localhost (Domain)
D [29/Aug/2021:16:58:51 +1000] [Client 20] Waiting for request.
I [29/Aug/2021:16:58:51 +1000] Expiring subscriptions...
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Active clients", busy="Active clients"
D [29/Aug/2021:16:58:51 +1000] [Client 21] Server address is "/run/cups/cups.sock".
D [29/Aug/2021:16:58:51 +1000] [Client 21] Accepted from localhost (Domain)
D [29/Aug/2021:16:58:51 +1000] [Client 21] Waiting for request.
D [29/Aug/2021:16:58:51 +1000] [Client 20] HTTP_STATE_WAITING Closing for error 32 (Broken pipe)
D [29/Aug/2021:16:58:51 +1000] [Client 20] Closing connection.
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Not busy", busy="Active clients"
D [29/Aug/2021:16:58:51 +1000] [Client 21] POST / HTTP/1.1
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Active clients", busy="Not busy"
D [29/Aug/2021:16:58:51 +1000] [Client 21] Read: status=200, state=6
D [29/Aug/2021:16:58:51 +1000] [Client 21] No authentication data provided.
D [29/Aug/2021:16:58:51 +1000] [Client 21] Read: status=100, state=6
...
D [29/Aug/2021:16:58:51 +1000] [Client 21] Read: status=100, state=6
D [29/Aug/2021:16:58:51 +1000] [Client 21] 2.0 CUPS-Get-Printers 1
D [29/Aug/2021:16:58:51 +1000] CUPS-Get-Printers
D [29/Aug/2021:16:58:51 +1000] [Client 21] Returning IPP successful-ok for CUPS-Get-Printers (no URI) from localhost.
D [29/Aug/2021:16:58:51 +1000] [Client 21] Content-Length: 915
D [29/Aug/2021:16:58:51 +1000] [Client 21] cupsdSendHeader: code=200, type="application/ipp", auth_type=0
D [29/Aug/2021:16:58:51 +1000] [Client 21] con->http=0x5587046eabc0
D [29/Aug/2021:16:58:51 +1000] [Client 21] cupsdWriteClient error=0, used=0, state=HTTP_STATE_POST_SEND, data_encoding=HTTP_ENCODING_LENGTH, data_remain
ing=915, response=0x5587046cf160(IPP_STATE_DATA), pipe_pid=0, file=-1
D [29/Aug/2021:16:58:51 +1000] [Client 21] Writing IPP response, ipp_state=IPP_STATE_DATA, old wused=0, new wused=0
D [29/Aug/2021:16:58:51 +1000] [Client 21] bytes=0, http_state=0, data_remaining=915
D [29/Aug/2021:16:58:51 +1000] [Client 21] Flushing write buffer.
D [29/Aug/2021:16:58:51 +1000] [Client 21] New state is HTTP_STATE_WAITING
D [29/Aug/2021:16:58:51 +1000] [Client 21] Waiting for request.
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Not busy", busy="Active clients"
D [29/Aug/2021:16:58:51 +1000] [Client 21] HTTP_STATE_WAITING Closing for error 32 (Broken pipe)
D [29/Aug/2021:16:58:51 +1000] [Client 21] Closing connection.
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Not busy", busy="Not busy"
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Active clients", busy="Not busy"
D [29/Aug/2021:16:58:51 +1000] [Client 22] Server address is "/run/cups/cups.sock".
D [29/Aug/2021:16:58:51 +1000] [Client 22] Accepted from localhost (Domain)
D [29/Aug/2021:16:58:51 +1000] [Client 22] Waiting for request.
D [29/Aug/2021:16:58:51 +1000] [Client 22] POST /printers/WorkForce-435 HTTP/1.1
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Active clients", busy="Active clients"
D [29/Aug/2021:16:58:51 +1000] [Client 22] Read: status=200, state=6
D [29/Aug/2021:16:58:51 +1000] [Client 22] No authentication data provided.
D [29/Aug/2021:16:58:51 +1000] [Client 22] Read: status=100, state=6
...
D [29/Aug/2021:16:58:51 +1000] [Client 22] Read: status=100, state=6
D [29/Aug/2021:16:58:51 +1000] [Client 22] 2.1 Print-Job 1
D [29/Aug/2021:16:58:51 +1000] [Client 22] Read: status=100, state=6
D [29/Aug/2021:16:58:51 +1000] [Client 22] Read: status=100, state=6
D [29/Aug/2021:16:58:51 +1000] Print-Job ipp://localhost:631/printers/WorkForce-435
D [29/Aug/2021:16:58:51 +1000] [Job ???] Auto-typing file...
I [29/Aug/2021:16:58:51 +1000] [Job ???] Request file type is application/pdf.
D [29/Aug/2021:16:58:51 +1000] Print-Job client-error-document-format-not-supported: Unsupported format \"application/pdf\".
E [29/Aug/2021:16:58:51 +1000] [Client 22] Returning IPP client-error-document-format-not-supported for Print-Job (ipp://localhost:631/printers/WorkForc
e-435) from localhost.
D [29/Aug/2021:16:58:51 +1000] [Client 22] Content-Length: 167
D [29/Aug/2021:16:58:51 +1000] [Client 22] cupsdSendHeader: code=200, type="application/ipp", auth_type=0
D [29/Aug/2021:16:58:51 +1000] [Client 22] con->http=0x558704697fa0
D [29/Aug/2021:16:58:51 +1000] [Client 22] cupsdWriteClient error=0, used=0, state=HTTP_STATE_POST_SEND, data_encoding=HTTP_ENCODING_LENGTH, data_remain
ing=167, response=0x558704683880(IPP_STATE_DATA), pipe_pid=0, file=-1
D [29/Aug/2021:16:58:51 +1000] [Client 22] Writing IPP response, ipp_state=IPP_STATE_DATA, old wused=0, new wused=0
D [29/Aug/2021:16:58:51 +1000] [Client 22] bytes=0, http_state=0, data_remaining=167
D [29/Aug/2021:16:58:51 +1000] [Client 22] Flushing write buffer.
D [29/Aug/2021:16:58:51 +1000] [Client 22] New state is HTTP_STATE_WAITING
D [29/Aug/2021:16:58:51 +1000] [Client 22] Waiting for request.
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Not busy", busy="Active clients"
D [29/Aug/2021:16:58:51 +1000] [Client 22] HTTP_STATE_WAITING Closing for error 32 (Broken pipe)
D [29/Aug/2021:16:58:51 +1000] [Client 22] Closing connection.
D [29/Aug/2021:16:58:51 +1000] cupsdSetBusyState: newbusy="Not busy", busy="Not busy"
我从 Epson 网站安装了一堆 DEB 文件：
epson-inkjet-printer-201109w_1.0.0-1lsb3.2_amd64.deb
epson-inkjet-printer-escpr_1.7.17-1lsb3.2_amd64.deb
epson-pc-fax_1.0.0-1lsb3.2_amd64.deb
epson-printer-utility_1.1.1-1lsb3.2_amd64.deb
可惜，无济于事。
我正在使用 Firefox（91.0.2 64 位）网络浏览器，单击网页上的“打印”图标。