python - 转义序列中断 pyserial 客户端

Question

我正在使用 pyserial 为网络设备编写客户端，它在登录设备后和在设备上收到提示之前挂起几秒钟。跟踪线上的字节，我看到以下转义序列是造成延迟的原因:

0003a0  73 65 20 6c 65 76 65 6c  0d 0a 0d 1b 5b 39 39 39       |se level....[999|
0003b0  39 42 0d 1b 5b 39 39 39  39 42 1b 5a 20 20 1b 5b       |9B..[9999B.Z  .[|
0003c0  36 6e 0d 0d 0d 0d 5b 61  64 6d 69 6e 40 73 77 69       |6n....[admin@swi|
0003d0  74 63 68 5d 20 3e 20 20  20 20 20 20 20 20 20 20       |tch] >          |

当使用 screen 连接到设备时，不会出现延迟，因为 screen 正在正确响应。

0003a0  73 65 20 6c 65 76 65 6c  0d 0a 0d 1b 5b 39 39 39       |se level....[999|
0003b0  39 42 0d 1b 5b 39 39 39  39 42 1b 5a 20                |9B..[9999B.Z    |

                                ---=== WRITE ===---
000000  1b 5b 3f 31 3b 32 63                                   |.[?1;2c         |

                                ---=== READ ===---
000000  20 1b 5b 36 6e                                         | .[6n           |

                                ---=== WRITE ===---
000000  1b 5b 35 37 3b 33 52                                   |.[57;3R         |

                                ---=== READ ===---
000000  1b 5b 34 6c 1b 5b 32 30  6c 1b 5b 3f 34 37 6c 1b       |.[4l.[20l.[?47l.|
000010  5b 3f 37 68 1b 5b 3f 35  6c 1b 5b 3f 32 35 68 1b       |[?7h.[?5l.[?25h.|
000020  5b 48 1b 5b 39 39 39 39  42 1b 5b 36 6e                |[H.[9999B.[6n   |

                                ---=== WRITE ===---
000000  1b 5b 35 37 3b 31 52                                   |.[57;1R         |

                                ---=== READ ===---
000000  1b 5b 48 1b 5b 39 39 39  39 42 1b 44 1b 5b 39 39       |.[H.[9999B.D.[99|
000010  39 39 41 1b 5b 36 6e                                   |99A.[6n         |

                                ---=== WRITE ===---
000000  1b 5b 31 3b 31 52                                      |.[1;1R          |

                                ---=== READ ===---
000000  1b 5b 48 1b 5b 39 39 39  39 43 1b 5b 36 6e             |.[H.[9999C.[6n  |

                                ---=== WRITE ===---
000000  1b 5b 31 3b 31 34 31 52                                |.[1;141R        |

                                ---=== READ ===---
000000  1b 5b 48 c4 9b 48 1b 5b  36 6e 0d 20 20 20             |.[H..H.[6n.     |

                                ---=== WRITE ===---
000000  1b 5b 31 3b 33 52                                      |.[1;3R          |

                                ---=== READ ===---
000000  1b 5b 48 1b 5b 39 39 39  39 43 1b 5b 36 6e 20 1b       |.[H.[9999C.[6n .|

                                ---=== WRITE ===---
000000  1b 5b 31 3b 31 34 31 52                                |.[1;141R        |

                                ---=== READ ===---
000000  5b 36 6e 20 1b 5b 36 6e                                |[6n .[6n        |

                                ---=== WRITE ===---
000000  1b 5b 31 3b 31 34 32 52  1b 5b 32 3b 32 52             |.[1;142R.[2;2R  |

                                ---=== READ ===---
000000  1b 5b 33 3b 35 72 1b 5b  48 1b 5b 36 6e 0a 0a          |.[3;5r.[H.[6n.. |
                               ---=== WRITE ===---
000000  1b 5b 31 3b 31 52                                      |.[1;1R          |

                                ---=== READ ===---
000000  0a 0a 0a 0a 0a 1b 5b 36  6e 1b 5b                      |......[6n.[     |

                                ---=== WRITE ===---
000000  1b 5b 35 3b 31 52                                      |.[5;1R          |

                                ---=== READ ===---
000000  39 39 39 39 42 1b 5b 36  6e 1b 5b 72                   |9999B.[6n.[r    |

                                ---=== WRITE ===---
000000  1b 5b 35 3b 31 52                                      |.[5;1R          |

                                ---=== READ ===---
000000  1b 5b 31 3b 39 39 39 39  72 0d 0d 0d 1b 5b 39 39       |.[1;9999r....[99|
000010  39 39 42 5b 61 64 6d 69  6e 40 73 77 69 74 63 68       |99B[admin@switch|
000020  5d 20 3e 20                                            |] >             |

这一系列转义序列到底在做什么，在我的客户端中处理这个问题的最佳方法是什么？

from asyncio import Protocol, get_event_loop
from serial.aio import create_serial_connection

class Serial(Protocol):

   def connection_made(self, transport):
       self.transport = transport

   def data_received(self, data):
       self.buffer += data.decode("utf-8")
       self.handle()

   def send(self, line):
       self.transport.write("{}\r\n".format(line).encode())

loop = get_event_loop()
coro = create_serial_connection(loop, Serial, "/dev/ttyUSB0")
loop.run_until_complete(coro)
loop.run_forever()

Answer 1

带有 [6n(及其前面的转义字符)的 block 要求终端告诉它光标在哪里，作为确定屏幕大小的一部分。显然 pyserial 不理解这一点，您必须等待一段时间，让执行请求的程序放弃并继续。

在XTerm Control Sequences :

CSI Ps n  Device Status Report (DSR).
...
            Ps = 6  -> Report Cursor Position (CPR) [row;column].

其中 CSI 是控制序列发起者 escape[.

当你运行 screen 时，它 interprets这个控制序列(即，它阅读、理解和适本地回复):

        case 'n':            if (a1 == 5)    /* Report terminal status */                Report(win, "\033[0n", 0, 0);            else if (a1 == 6)   /* Report cursor position */                Report(win, "\033[%d;%dR", win->w_y + 1, win->w_x + 1);

The status report control sequence is used by a few programs such as resize to determine the size of your terminal's screen. It works by moving the cursor to an impossibly far lower-right-corner, and then (because terminals have limits) asking how far it got. This particular example is not using resize, which sends 999 for each coordinate (but it's debatable whether there's a real scenario where four digits are needed).

The application that is sending the device status control sequence moves the cursor down with the escape[9999B, and apparently uses that later when setting up scrolling margins with the sequence ending with r. This is a frequently-used VT100 feature not in ECMA-48 (the r denotes a private use sequence, i.e., not standardized).

If you give it a bogus value for the cursor position, you might get poor results.

It also tries with two different control sequences to move the cursor to the home (upper-left) in this sequence from the screen read/writes:

1b 5b 48 c4 9b 48

(0x9b 是 0x1b、0x5b 或 escape 的 8 位等价物/kbd>[).

所以你的选择很少:

• 消除(可能不必要的)屏幕尺寸查询，或者
• 修改您的 pyserial 脚本以处理设备状态控制序列