Failed to paste more than 2035 characters with libwebsockets >= 4.4.0 #1532

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1. erusc

   added

   bug

   on Apr 24, 2026
2. erusc

   changed the title [-]Failed to paste more than 2035 characters with libwebsockets > 4.4.0[/-] [+]Failed to paste more than 2035 characters with libwebsockets >= 4.4.0[/+] on Apr 25, 2026
3. PvH-SPC commented on May 11, 2026

   

   PvH-SPC

   on May 11, 2026

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   Hi wondering what the plan is for this fix?
4. erusc commented on May 12, 2026

   

   erusc

   on May 12, 2026

   Author

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   I think I found the fix without hacking libwebsockets.

   diff --git a/src/protocol.c b/src/protocol.c
   index adb7d63..cd5d40d 100644
   --- a/src/protocol.c
   +++ b/src/protocol.c
   @@ -252,6 +252,9 @@ int callback_tty(struct lws *wsi, enum lws_callback_reasons reason, void *user,
    
          lws_get_peer_simple(lws_get_network_wsi(wsi), pss->address, sizeof(pss->address));
          lwsl_notice("WS   %s - %s, clients: %d\n", pss->path, pss->address, server->client_count);
   +#ifndef LWS_WITHOUT_EXTENSIONS
   +      lws_set_extension_option(wsi, "permessage-deflate", "rx_buf_size", "31");
   +#endif
          break;
    
        case LWS_CALLBACK_SERVER_WRITEABLE:
   diff --git a/src/server.c b/src/server.c
   index 183fa3a..13b3e81 100644
   --- a/src/server.c
   +++ b/src/server.c
   @@ -28,7 +28,7 @@ extern int callback_tty(struct lws *wsi, enum lws_callback_reasons reason, void
    
    // websocket protocols
    static const struct lws_protocols protocols[] = {{"http-only", callback_http, sizeof(struct pss_http), 0},
   -                                                 {"tty", callback_tty, sizeof(struct pss_tty), 0},
   +                                                 {"tty", callback_tty, sizeof(struct pss_tty), 2147483648},
                                                     {NULL, NULL, 0, 0}};
    
    #ifndef LWS_WITHOUT_EXTENSIONS

   The theoretical limit of rx buffer is 2^31 = 2147483648 (unsigned int, 2 GiB), according to https://github.com/warmcat/libwebsockets/blob/6a2542d/lib/roles/ws/ext/extension-permessage-deflate.c#L53-L66 and https://github.com/warmcat/libwebsockets/blob/6a2542d/lib/roles/ws/ext/extension-permessage-deflate.c#L232-L235.

   lws_set_extension_option only sets the soft cap, the actual limit is bound by protocol->rx_buffer_size or pt_serv_buf_size (when protocol->rx_buffer_size is 0).

   Kind of confusing that extension option rx_buf_size is the exponent of 2, while protocol->rx_buffer_size and pt_serv_buf_size is in bytes.

   The only problem is that I am not sure if it's ok to hardcode the number.
5. PvH-SPC commented on May 14, 2026

   

   PvH-SPC

   on May 14, 2026

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   Can we get this cut into a release? Not sure what changed but anything is better than the very small paste window we have now.
6. erusc commented on May 15, 2026

   

   erusc

   on May 15, 2026

   Author

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   For now you can just use 1.7.7 or build with libwebsockets 4.3.10.

   BUILD_TARGET=$(arch) LIBWEBSOCKETS_VERSION=4.3.10 ./scripts/cross-build.sh

   Set BUILD_TARGET if you need a different architecture.

   ttyd/scripts/cross-build.sh

   Lines 201 to 219 in 647d55a

   	case ${BUILD_TARGET} in
   	i686|x86_64|aarch64|mips|mipsel|mips64|mips64el|powerpc64|powerpc64le|s390x)
   	build "${BUILD_TARGET}-linux-musl" "${BUILD_TARGET}"
   	;;
   	arm)
   	build "${BUILD_TARGET}-linux-musleabi" "${BUILD_TARGET}"
   	;;
   	armhf)
   	build arm-linux-musleabihf "${BUILD_TARGET}"
   	;;
   	armv7l)
   	build armv7l-linux-musleabihf "${BUILD_TARGET}"
   	;;
   	win32)
   	build x86_64-w64-mingw32 "${BUILD_TARGET}"
   	;;
   	*)
   	echo "unknown cross target: ${BUILD_TARGET}" && exit 1
   	esac

   v4.3.10 was tagged 2 months ago, so I assume it's not outdated yet.

   p.s.
   There seem to be another issue about TLS with libwebsockets 4.4 and 4.5, so it might be better to stick with 4.3.x for the time being.