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description=Mobile shell that supports roaming and intelligent local echo. Like SSH secure shell, but allows mobility and more responsive and robust.;
author=Keith Winstein mosh-devel@mit.edu ;

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Text of the page (random words):
nstructions install from your package manager macos 10 10 or later binary package mosh 1 4 0 pkg this is a standalone os x package that will work on any supported macintosh however if you are using a package manager such as homebrew or macports we suggest using it to get mosh for better compatibility and automatic updates homebrew os x 10 5 or later brew install mosh macports os x 10 5 or later sudo port install mosh windows install mosh for chrome there is no native mosh executable for windows available at this time the chrome version of mosh is the easiest way to use mosh on windows cygwin c setup exe q mosh mosh on cygwin uses openssh and is suitable for windows users with advanced ssh configurations mosh is not compatible with cygwin s built in windows console terminal emulation you will need to run mosh from a full featured terminal program such as mintty rxvt putty or an x11 terminal emulator android install juicessh from the play store or install termux from f droid chrome chrome os install mosh for chrome ios install blink shell from the app store or build it from source alpine linux apk add mosh arch linux pacman s mosh debian squeeze backports and later sudo apt get install mosh fedora 15 or later sudo dnf install mosh gentoo emerge net misc mosh guixsd guix package i mosh mosh is also available through guix when installed on other linux distributions opensuse 12 3 or later sudo zypper in mosh ubuntu 12 04 and later sudo apt get install mosh the ppa keithw mosh dev ppa tracks the development version of mosh freebsd pkg install net mosh openbsd pkg_add mosh netbsd pkgsrc cd net mosh make install clean opencsw solaris 10 update 8 or later pkgutil i mosh operating system logos are trademarks or registered trademarks and are displayed for identification only the vendors shown aren t affiliated with and haven t endorsed mosh building from source latest release extract mosh 1 4 0 tar gz sha 256 in signed release announcement then cd mosh 1 4 0 configure make make install compiling from git git clone https github com mobile shell mosh cd mosh autogen sh configure make make install dependencies debian control in git includes an authoritative list of build dependencies name typical package perl 5 14 or newer perl protocol buffers protobuf compiler libprotobuf dev ncurses libncurses5 dev zlib zlib1g dev utempter optional libutempter dev openssl libssl dev additionally pkg config is a build only dependency on most systems security on new operating systems note that mosh client receives an aes session key as an environment variable if you are porting mosh to a new operating system please make sure that a running process s environment variables are not readable by other users we have confirmed that this is the case on gnu linux os x and freebsd usage replaces interactive ssh instant keystroke response robust to roaming but you ll need working udp typical usage mosh chewbacca norad mil mosh will log the user in via ssh then start a connection on a udp port between 60000 and 61000 different username mosh potus ackbar bls gov server binary outside path mosh server tmp mosh server r2d2 the user can specify an alternate path for the mosh server on the remote host the server binary can even be installed in the user s home directory selecting mosh udp port mosh p 1234 darth useful when the server is behind a port forwarder or nat selecting ssh port mosh ssh ssh p 2222 figrindan other ssh options mosh ssh bin ssh i identity fett disable instant echo mosh predict never niennunb the n switch is a synonym by contrast passing predict always or a will enable instant local echo even on low delay links with a command mosh pello screen dr this reattaches to a long running screen session ending the connection normally logout or exit on the remote host will close the session mosh accepts the escape sequence ctrl typically typed with control shift 6 then a period to end the connection forcibly to send a literal ctrl type ctrl manual more details can be found in the mosh 1 mosh client 1 and mosh server 1 manual pages technical info papers the mosh research paper describes the design and evaluation of mosh in more detail than you may want the paper was presented at the 2012 usenix annual technical conference held june 13 15 2012 in sunny boston mass in addition the mosh a state of the art good old fashioned mobile shell essay gives further information about the design principles behind mosh including the prophylactic retransmission technique the essay was published in usenix login magazine august 2012 iso 2022 locking escape sequences oh flying spaghetti monster please kill me now actual usenix peer review from the mosh paper why you should trust mosh with your remote terminal needs we worry about details so obscure even usenix reviewers don t want to hear about them how mosh works remote shell protocols traditionally work by conveying a byte stream from the server to the client to be interpreted by the client s terminal this includes telnet rlogin and ssh mosh works differently and at a different layer with mosh the server and client both maintain a snapshot of the current screen state the problem becomes one of state synchronization getting the client to the most recent server side screen as efficiently as possible this is accomplished using a new protocol called the state synchronization protocol for which mosh is the first application ssp runs over udp synchronizing the state of any object from one host to another datagrams are encrypted and authenticated using aes 128 in ocb3 mode while ssp takes care of the networking protocol it is the implementation of the object being synchronized that defines the ultimate semantics of the protocol roaming with ssp becomes easy the client sends datagrams to the server with increasing sequence numbers including a heartbeat at least once every three seconds every time the server receives an authentic packet from the client with a sequence number higher than any it has previously received the ip source address of that packet becomes the server s new target for its outgoing packets by doing roaming statelessly in this manner roaming works in and out of nats even ones that may themselves be roaming roaming works even when the client is not aware that its internet visible ip address has changed the heartbeats allow mosh to inform the user when it hasn t heard from the server in a while unlike ssh where users may be unaware of a dropped connection until they try to type mosh runs two copies of ssp one in each direction of the connection the connection from client to server synchronizes an object that represents the keys typed by the user and with tcp like semantics the connection from server to client synchronizes an object that represent the current screen state and the goal is always to convey the client to the most recent server side state possibly skipping intermediate frames because ssp works at the object layer and can control the rate of synchronization in other words the frame rate it does not need to send every byte it receives from the application that means mosh can regulate the frames so as not to fill up network buffers retaining the responsiveness of the connection and making sure control c always works quickly protocols that must send every byte can t do this careful terminal emulation one benefit of working at the terminal layer was the opportunity to build a clean utf 8 terminal emulator from scratch mosh fixes several unicode bugs in existing terminals and in ssh and was designed as a fresh start to try to be robust and correct even for pathological inputs tricky unicode only mosh and the os x terminal correctly handle a unicode combining character in the first column xterm circumflex on wrong letter gnome terminal no circumflex at all os x terminal app gets it right mosh gets it right too iso 2022 locking escapes only mosh will never get stuck in hieroglyphs when a nasty program writes to the terminal see markus kuhn s discussion of the relationship between iso 2022 and utf 8 xterm gnome terminal os x terminal app mosh evil escape sequences only mosh and gnome terminal have a defensible rendering when unicode mixes with an ecma 48 ansi escape sequence the os x terminal unwisely tries to normalize its input before the vt500 state machine causing it to misinterpret and become unusable after receiving the following input this also means the os x terminal s interpretation of the incoming octet stream varies depending on how the incoming octets are split across tcp segments because the normalization only looks ahead to available bytes we earlier wrote that this misbehaving sequence crashes the os x terminal app this was mistaken instead terminal app interprets the escape sequence as shutting off keyboard input and because of an unrelated bug in terminal app it is not possible for the user to restore keyboard input by resetting the terminal from the menu xterm circumflex on wrong letter gnome terminal s circumflex placement is defensible os x terminal app applies circumflex to part of escape sequence then irretrievably shuts off keyboard input mosh gets this one right mosh sets iutf8 in the posix framework the kernel needs to know whether the user is typing in an 8 bit character set or in utf 8 because in canonical mode i e cooked mode the kernel needs to be able to delete a typed multibyte character sequence from an input buffer on os x and linux this is done with the iutf8 termios flag see diagnostic explaining the need for this flag mosh sets the iutf8 flag when possible and stubbornly refuses to start up unless the user has a utf 8 clean environment ssh does not set the iutf8 flag which can lead to garbage in input buffers instant local echo and line editing the other major benefit of working at the terminal emulation layer is that the mosh client is free to scribble on the local screen without lasting consequence we use this to implement intelligent local echo the client runs a predictive model in the background of the server s behavior hypothesizing that each keystroke will be echoed at the cursor location and that the backspace and left and right arrow keys will have their traditional effect but only when a prediction is confirmed by the server are these effects actually shown to the user in addition by default predictions are only displayed on high delay connections or during a network glitch predictions are done in epochs when the user does something that might alter the echo behavior like hit esc or carriage return or an up or down arrow mosh goes back into making background predictions until a prediction from the new batch can be confirmed as correct thus unlike previous attempts at local echo with telnet and rlogin mosh s local echo can be used everywhere even in full screen programs like emacs and vi real world benefits we evaluated mosh using traces contributed by six users covering about 40 hours of real world usage and including 9 986 total keystrokes these traces included the timing and contents of all writes from the user to the host and vice versa the users were asked to contribute typical real world sessions in practice the traces include use of popular programs such as the bash shell and zsh shells the alpine and mutt e mail clients the emacs and vim text editors the irssi and barnowl chat clients the links text mode web browser and several programs unique to each user to evaluate typical usage of a mobile terminal we replayed the traces over an otherwise unloaded sprint commercial ev do 3g cellular internet connection in cambridge mass a client side process played the user portion of the traces and a server side process waited for the expected user input and then replied in time with the prerecorded server output we speeded up long periods with no activity the average round trip time on the link was about half a second we replayed the traces over two different transports ssh and mosh and recorded the user interface response latency to each simulated user keystroke the mosh predictive algorithm was frozen prior to collecting the traces and was not adjusted in response to their contents or results the results cumulative distribution of keystroke response times with sprint ev do 3g internet service mosh reduced the median keystroke response time from 503 ms to nearly instant because more than 70 of the keystrokes could be immediately displayed and reduced the mean keystroke response time from 515 ms to 173 ms qualitatively mosh makes remote servers feel more like the local machine frequently asked questions q who wrote mosh mosh was written by keith winstein along with anders kaseorg quentin smith richard tibbetts keegan mcallister and john hood q why another remote terminal protocol practical latency on the internet is on the increase with the rise of bufferbloat and sophisticated wireless links that optimize for throughput over delay and roaming is more common than ever now that laptops and handheld devices have largely displaced desktops ssh is great but frustrating to use when you want to change ip addresses or have a long delay link or a dodgy connection moreover telnet had some good things going for it a local echo mode and a well defined network virtual terminal even today ssh doesn t properly support utf 8 end to end on a posix system q are the mosh principles relevant to other network applications we think so the design principles that mosh stands for are conservative warning the user if the state being displayed is out of date serializing and checkpointing all transactions so that if there are no warnings the user knows every prior transaction has succeeded and handling expected events like roaming from one wifi network to another gracefully those don t seem too controversial but fancy apps like gmail in chromium or on android still behave atrociously on dodgy connections or after switching ip addresses have you ever had gmail leave an e mail message in sending for ten hours while merrily retrieving new mail and not indicating any kind of error us too we think there may be considerable room for improvement in many network user interfaces from the application of these values q i m getting mosh requires a utf 8 locale how can i fix this to diagnose the problem run locale on the local terminal and ssh remotehost locale to use mosh both sides of the connection will need to show a utf 8 locale like lc_ctype en_us utf 8 on many systems ssh will transfer the locale related environment variables which are then inherited by mosh server if this mechanism fails mosh as of version 1 2 will pass the variables itself if neither mechanism is successful you can do something like mosh remotehost server lang en_us utf 8 mosh server if en_us utf 8 does not exist on the remote server you can replace this with a utf 8 locale that does exist you may also need to set lang locally for the benefit of mosh client it is possible that the local and remote machines will need different l...