Bcvi allows running a full-screen vi editor session over a limited bandwidth or high-latency connection, such as a serial console or SSH connection with significant lag. It achieves this by using a "back-channel" to send screen updates efficiently. Instead of redrawing the entire screen for every change, bcvi only transmits the differences, leading to a significantly more responsive experience. This makes editing files remotely over constrained connections practical, providing a near-native vi experience even with limited bandwidth. The back-channel can be another SSH connection or even a separate serial port, providing flexibility in setup.
The article "bcvi – run vi over a 'back-channel'" describes a novel approach to editing files remotely over a constrained network connection, specifically targeting situations where using tools like SSH or VNC might be impractical due to bandwidth limitations or latency issues. The core concept revolves around establishing a "back-channel" which is a separate, lower-bandwidth communication pathway alongside the primary channel being used for other purposes. This back-channel is then leveraged by a custom-designed program called bcvi to facilitate remote file editing using the familiar Vi editor interface.
The article details the technical implementation of bcvi, explaining how it functions as a proxy between the user's local Vi instance and the remote file. Instead of transmitting the entire screen or file content back and forth, bcvi only exchanges minimal information necessary for Vi's operation. This includes keystrokes entered by the user, cursor movements, and changes to the file's buffer. The program achieves this efficiency by hooking into Vi's internal functions to intercept and process these events. On the remote end, a corresponding component of bcvi interprets the transmitted commands and applies them to the target file. The resulting changes are then relayed back to the local Vi instance, updating the user's view accordingly.
The back-channel communication itself is handled through a separate program called bc, which utilizes User Datagram Protocol (UDP) for its transport. This choice is motivated by the desire to minimize overhead and tolerate occasional packet loss, making it suitable for unreliable network conditions. The bc program encapsulates the Vi-specific commands and data within UDP packets, ensuring efficient and robust transmission over the back-channel.
The article highlights several advantages of using bcvi. The reduced bandwidth consumption makes it ideal for slow or intermittent connections. The responsiveness, despite potentially high latency, is attributed to the asynchronous nature of the communication. The familiarity of the Vi interface offers a comfortable and efficient editing experience for users already accustomed to Vi's commands and workflows. The article further emphasizes the portability of bcvi, stating its compatibility with various Unix-like systems and its reliance on readily available tools like Vi and UDP.
Finally, the article discusses the potential use cases for bcvi, such as editing configuration files on embedded devices or managing files on remote servers with limited connectivity. It also touches upon the inherent limitations of the approach, acknowledging the potential impact of significant packet loss on the editing experience and the assumption that the remote system has a compatible version of Vi installed. The overall tone suggests that bcvi offers a practical and efficient solution for remote file editing in specific, constrained environments.
Summary of Comments ( 13 )
https://news.ycombinator.com/item?id=43283814
Hacker News users discuss the cleverness and potential uses of
bcvi, particularly for embedded systems debugging. Some express admiration for the ingenuity of using the back channel for editing, highlighting its usefulness when other methods are unavailable. Others question the practicality due to potential slowness and limitations, suggesting alternatives likeed. A few commenters reminisce about using similar techniques in the past, emphasizing the historical context of this approach within resource-constrained environments. Some discuss potential security implications, pointing out that the back channel could be vulnerable to manipulation. Overall, the comments appreciate the technical ingenuity while acknowledging the niche appeal ofbcvi.The Hacker News post "Bcvi – run vi over a 'back-channel' (2010)" has several comments discussing the utility and implications of the
bcvitool.One commenter highlights the potential security risks of using such a tool, especially if the back channel isn't adequately secured. They express concern about inadvertently exposing sensitive information or granting unintended access to a system. This concern is echoed by another user who points out the inherent danger of trusting arbitrary escape sequences. They suggest that, while interesting, the approach presents a significant attack surface.
Another commenter questions the practical applications of
bcvi, wondering in what scenarios it would be genuinely useful. They acknowledge the cleverness of the concept but struggle to envision situations where it would be preferable to established methods of remote file editing. This skepticism is shared by a separate commenter who points out the existing availability of tools likesshfswhich offer a more robust and secure way to edit remote files.Several commenters delve into the technical aspects of
bcvi, discussing its implementation and potential limitations. One points out the challenge of handling interactive commands and the need for careful consideration of terminal emulation. Another user mentions the project's age and expresses curiosity about its current status and whether it's still actively maintained.A commenter recalls using a similar technique in the past, involving
screenandvi, for editing files over a serial console. They describe the setup and the advantages it offered in their specific use case. This anecdote provides a practical example of a scenario where a back-channel editing approach could be beneficial.One commenter humorously suggests using netcat as a more straightforward alternative for editing remote files over a simple connection. While likely intended as a tongue-in-cheek suggestion, it highlights the potential simplicity of achieving similar functionality with readily available tools.
Finally, a few comments express general appreciation for the cleverness and ingenuity of the
bcviconcept, even if its practicality is debated. They acknowledge the value of exploring unconventional approaches to problem-solving.