Keith Winstein
97 lines
3.5 KiB
Plaintext
97 lines
3.5 KiB
Plaintext
Mosh -- the mobile shell
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Mosh is a remote terminal application that supports intermittent
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connectivity, allows roaming, and provides speculative local echo
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and line editing of user keystrokes.
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It aims to support the typical interactive uses of SSH, plus:
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* Mosh keeps the session alive if the client goes to sleep and
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wakes up later, or temporarily loses its Internet connection.
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* Mosh allows the client and server to "roam" and change IP
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addresses, while keeping the connection alive. Unlike SSH, Mosh
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can be used while switching between Wi-Fi networks or from Wi-Fi
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to cellular data to wired Ethernet.
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* The Mosh client runs a predictive model of the server's behavior
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in the background and tries to guess intelligently how each
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keystroke will affect the screen state. When it is confident in
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its predictions, it will show them to the user while waiting for
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confirmation from the server. Most typing and uses of the left-
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and right-arrow keys can be echoed immediately.
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As a result, Mosh is usable on high-latency links, e.g. on a
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cellular data connection or spotty Wi-Fi. In distinction from
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previous attempts at local echo modes in other protocols, Mosh
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works properly with full-screen applications such as emacs, vi,
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alpine, and irssi, and automatically recovers from occasional
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prediction errors within an RTT. On high-latency links, Mosh
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underlines its predictions while they are outstanding and removes
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the underline when they are confirmed by the server.
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Mosh does not support X forwarding or the non-interactive uses of SSH,
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including port forwarding.
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Other features:
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* Mosh adjusts its frame rate so as not to fill up network queues
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on slow links, so "Control-C" always works within an RTT to halt
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a runaway process.
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* Mosh warns the user when it has not heard from the server
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in a while.
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* Mosh supports lossy links that lose a significant fraction
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of their packets.
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* Mosh handles some Unicode edge cases better than SSH and existing
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terminal emulators by themselves, but requires a UTF-8
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environment to run.
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* Mosh leverages SSH to set up the connection and authenticate
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users. Mosh does not contain any privileged (root) code.
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Usage:
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The mosh-client binary must be installed on the user's machine, and
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the mosh-server binary on the remote host.
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The user runs:
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$ mosh [user@]host
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If the mosh-client or mosh-server binaries are installed outside the
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user's PATH, mosh accepts the arguments --client=PATH and
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--server=PATH to select alternate locations.
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How it works:
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The mosh program will SSH to user@host to establish the connection.
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SSH may prompt the user for a password or use public-key
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authentication to log in.
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From this point, mosh runs the 'mosh-server' process (as the user)
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on the server machine. The server process listens on a high UDP port
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and sends its port number and an AES-128 secret key back to the
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client over SSH. The SSH connection is then shut down and the
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terminal session begins over UDP.
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If the client changes IP addresses, the server will begin sending
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to the client on the new IP address within a few seconds.
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To function, Mosh requires high-port UDP datagrams to be passed
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between client and server. Sites that have these ports firewalled
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would not be able to use Mosh.
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More info:
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* Mosh Web site:
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http://mosh.mit.edu
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* mosh-users@mit.edu mailing list:
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http://mailman.mit.edu/mailman/listinfo/mosh-users
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