[vim/vim] revenge: Add ch_listen() function for socket server support (PR #19231)

mattn

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Jan 21, 2026, 5:09:31 AM (4 days ago) Jan 21

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Summary

This patch adds ch_listen() function to Vim, allowing scripts to create listening sockets and accept incoming network connections. This enables Vim to act as a simple network server for various use cases.

Changes

New Functions

ch_listen(address [, options]) - Listen on a socket and accept connections
- Returns a channel representing the listening socket
- Calls a callback function when a new client connects
- Supports both IPv4 and Unix domain sockets
channel_listen_unix(path, callback) - Unix domain socket support
channel_listen_func(argvars) - Vim script interface

Implementation Details

Added ch_listen field to struct channel_S to mark listening sockets
Modified channel_read() to handle accept() on listening sockets
When a connection is accepted, a new channel is created and passed to the callback
The callback receives the accepted channel and client address

API Usage

function! OnConnect(channel, address)
    echomsg 'Client connected from: ' . a:address
    call ch_setoptions(a:channel, {
        \ 'callback': function('OnData'),
    \ })
endfunction

function! OnData(channel, data)
    echomsg 'Received: ' . a:data
endfunction

let server = ch_listen('127.0.0.1:8080', {
    \ 'callback': function('OnConnect'),
\ })

Use Cases

Simple HTTP server for serving static files
Network protocol implementation for testing
Local IPC between Vim and other processes
Learning network programming concepts

Testing

Implemented test case Test_listen() in test_channel.vim
Tested with multiple concurrent connections
Verified callback invocation and data transmission

Related Features

This complements the existing ch_open() function:

ch_open() - connect to a server
ch_listen() - accept connections as a server

Limitations

No SSL/TLS support
Single-threaded (blocks Vim event loop during processing)
No built-in HTTP parsing (simple callbacks only)

This is demonstration of HTTP server written in Vim script.

image.png (view on web)

You can view, comment on, or merge this pull request online at:

https://github.com/vim/vim/pull/19231

Commit Summary

61d4cda support ch_listen

File Changes

(7 files)

Patch Links:

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mattn

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Jan 21, 2026, 5:21:40 AM (4 days ago) Jan 21

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mattn left a comment (vim/vim#19231)

I'll fix test fail in later.

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mattn

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Jan 21, 2026, 5:46:04 AM (4 days ago) Jan 21

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@mattn pushed 1 commit.

2d56f55 fix build

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mattn

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Jan 21, 2026, 5:53:09 AM (4 days ago) Jan 21

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@mattn pushed 1 commit.

bf360c4 remove is_ipv6 unused

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mattn

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Jan 21, 2026, 6:05:08 AM (4 days ago) Jan 21

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28d6f7a fix pro file

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mattn

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Jan 21, 2026, 6:09:51 AM (4 days ago) Jan 21

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2fe4734 fix build

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mattn

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Jan 21, 2026, 6:20:55 AM (4 days ago) Jan 21

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72aaa64 fix indent

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mattn

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Jan 21, 2026, 6:32:43 AM (4 days ago) Jan 21

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d0ff4c9 fix function index

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mattn

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Jan 21, 2026, 6:34:10 AM (4 days ago) Jan 21

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b37fc0f fix indent

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mattn

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Jan 21, 2026, 7:02:08 AM (4 days ago) Jan 21

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58661c8 fix order in function list

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mattn

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Jan 21, 2026, 7:10:25 AM (4 days ago) Jan 21

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c61af31 fix indent

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mattn

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Jan 21, 2026, 7:51:53 AM (4 days ago) Jan 21

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95c7100 call clear_tv

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Christian Brabandt

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Jan 21, 2026, 2:32:48 PM (4 days ago) Jan 21

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chrisbra left a comment (vim/vim#19231)

Thanks that is nice. But I'll move this after the Vim 9.2 release.
Can a few people try it out? I'd also think that we should have a very simple practical example for this in the help.

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bfrg

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Jan 24, 2026, 12:41:35 PM (23 hours ago) Jan 24

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bfrg left a comment (vim/vim#19231)

It is not clear from the docs how ch_listen() differs from ch_open({address} [, {options}])? See :h channel-address for possible values of address.

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mattn

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Jan 24, 2026, 2:01:37 PM (22 hours ago) Jan 24

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mattn left a comment (vim/vim#19231)