TCP multi-client mode does not work

[GermanGeraskin]

What I was trying to accomplish

I am trying to transfer video data via TCP connection.

The problem I encountered

FFmpeg resets the TCP connection if the "multi-client" mode is used (listen=2).

The documentation https://ffmpeg.org/ffmpeg-all.html#tcp states the following:

listen=2|1|0

Listen for an incoming connection. 0 disables listen, 1 enables listen in single client mode, 2 enables listen in multi-client mode. Default value is 0.

The exact command line I am using

ffmpeg server:

./ffmpeg \
-v 9 \
-loglevel 99 \
-f rawvideo \
-video_size 1920x1080 \
-pixel_format yuv420p \
-framerate 25 \
-i 'tcp://127.0.0.1:19010?listen=2' \
-pix_fmt yuv420p \
-c:v h264_nvenc \
-preset p4 \
-rc vbr \
-cq 30 \
-an \
-f flv \
rtmp://127.0.0.1:1935/temp/qqq

ffmpeg client:

./ffmpeg \
-v 9 \
-loglevel 99 \
-f decklink \
-format_code Hp25 \
-i 'DeckLink Quad (1)' \
-pix_fmt yuv420p \
-r 25 \
-f rawvideo \
tcp://127.0.0.1:19010?tcp_nodelay=1

Console output

ffmpeg server:

 ./ffmpeg \
> -v 9 \
> -loglevel 99 \
> -f rawvideo \
> -video_size 1920x1080 \
> -pixel_format yuv420p \
> -framerate 25 \
> -i 'tcp://127.0.0.1:19010?listen=2' \
> -pix_fmt yuv420p \
> -c:v h264_nvenc \
> -preset p4 \
> -rc vbr \
> -cq 30 \
> -an \
> -f flv \
> rtmp://127.0.0.1:1935/temp/qqq
ffmpeg version n7.0.2 Copyright (c) 2000-2024 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: --pkg-config-flags=--static --extra-cflags=-I/usr/include/DeckLink --extra-libs='-lpthread -lm -ldl' --ld=g++ --enable-gpl --enable-nonfree --enable-pthreads --enable-avfilter --enable-libx264 --enable-nvenc --enable-decklink --enable-ffplay --enable-libzmq --enable-gnutls --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265
  libavutil      59.  8.100 / 59.  8.100
  libavcodec     61.  3.100 / 61.  3.100
  libavformat    61.  1.100 / 61.  1.100
  libavdevice    61.  1.100 / 61.  1.100
  libavfilter    10.  1.100 / 10.  1.100
  libswscale      8.  1.100 /  8.  1.100
  libswresample   5.  1.100 /  5.  1.100
  libpostproc    58.  1.100 / 58.  1.100
Splitting the commandline.
Reading option '-v' ... matched as option 'v' (set logging level) with argument '9'.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument '99'.
Reading option '-f' ... matched as option 'f' (force container format (auto-detected otherwise)) with argument 'rawvideo'.
Reading option '-video_size' ... matched as AVOption 'video_size' with argument '1920x1080'.
Reading option '-pixel_format' ... matched as AVOption 'pixel_format' with argument 'yuv420p'.
Reading option '-framerate' ... matched as AVOption 'framerate' with argument '25'.
Reading option '-i' ... matched as input url with argument 'tcp://127.0.0.1:19010?listen=2'.
Reading option '-pix_fmt' ... matched as option 'pix_fmt' (set pixel format) with argument 'yuv420p'.
Reading option '-c:v' ... matched as option 'c' (select encoder/decoder ('copy' to copy stream without reencoding)) with argument 'h264_nvenc'.
Reading option '-preset' ... matched as AVOption 'preset' with argument 'p4'.
Reading option '-rc' ... matched as AVOption 'rc' with argument 'vbr'.
Reading option '-cq' ... matched as AVOption 'cq' with argument '30'.
Reading option '-an' ... matched as option 'an' (disable audio) with argument '1'.
Reading option '-f' ... matched as option 'f' (force container format (auto-detected otherwise)) with argument 'flv'.
Reading option 'rtmp://127.0.0.1:1935/temp/qqq' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option v (set logging level) with argument 9.
Successfully parsed a group of options.
Parsing a group of options: input url tcp://127.0.0.1:19010?listen=2.
Applying option f (force container format (auto-detected otherwise)) with argument rawvideo.
Successfully parsed a group of options.
Opening an input file: tcp://127.0.0.1:19010?listen=2.
[rawvideo @ 0x555b20ecc040] Opening 'tcp://127.0.0.1:19010?listen=2' for reading
[tcp @ 0x555b20ecc8c0] No default whitelist set
[rawvideo @ 0x555b20ecc040] Before avformat_find_stream_info() pos: 0 bytes read:0 seeks:0 nb_streams:1
[rawvideo @ 0x555b20ecc040] stream 0: start_time: NOPTS duration: NOPTS
[rawvideo @ 0x555b20ecc040] format: start_time: NOPTS duration: NOPTS (estimate from bit rate) bitrate=622080 kb/s
[rawvideo @ 0x555b20ecc040] After avformat_find_stream_info() pos: 0 bytes read:0 seeks:0 frames:0
Input #0, rawvideo, from 'tcp://127.0.0.1:19010?listen=2':
  Duration: N/A, bitrate: 622080 kb/s
  Stream #0:0, 0, 1/25: Video: rawvideo, 1 reference frame (I420 / 0x30323449), yuv420p, 1920x1080, 0/1, 622080 kb/s, 25 tbr, 25 tbn
Successfully opened the file.
Parsing a group of options: output url rtmp://127.0.0.1:1935/temp/qqq.
Applying option pix_fmt (set pixel format) with argument yuv420p.
Applying option c:v (select encoder/decoder ('copy' to copy stream without reencoding)) with argument h264_nvenc.
Applying option an (disable audio) with argument 1.
Applying option f (force container format (auto-detected otherwise)) with argument flv.
Successfully parsed a group of options.
Opening an output file: rtmp://127.0.0.1:1935/temp/qqq.
[out#0/flv @ 0x555b20edecc0] No explicit maps, mapping streams automatically...
[vost#0:0/h264_nvenc @ 0x555b20edf980] Created video stream from input stream 0:0
[rtmp @ 0x555b20f00240] No default whitelist set
[tcp @ 0x555b20effdc0] No default whitelist set
[tcp @ 0x555b20effdc0] Original list of addresses:
[tcp @ 0x555b20effdc0] Address 127.0.0.1 port 1935
[tcp @ 0x555b20effdc0] Interleaved list of addresses:
[tcp @ 0x555b20effdc0] Address 127.0.0.1 port 1935
[tcp @ 0x555b20effdc0] Starting connection attempt to 127.0.0.1 port 1935
[tcp @ 0x555b20effdc0] Successfully connected to 127.0.0.1 port 1935
[rtmp @ 0x555b20f00240] Handshaking...
[rtmp @ 0x555b20f00240] Type answer 3
[rtmp @ 0x555b20f00240] Server version 3.0.1.1
[rtmp @ 0x555b20f00240] Proto = rtmp, path = /temp/qqq, app = temp, fname = qqq
[rtmp @ 0x555b20f00240] Window acknowledgement size = 2500000
[rtmp @ 0x555b20f00240] Max sent, unacked = 2500000
[rtmp @ 0x555b20f00240] New incoming chunk size = 4096
[rtmp @ 0x555b20f00240] Releasing stream...
[rtmp @ 0x555b20f00240] FCPublish stream...
[rtmp @ 0x555b20f00240] Creating stream...
[rtmp @ 0x555b20f00240] Sending publish command for 'qqq'
Successfully opened the file.
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (h264_nvenc))
[vost#0:0/h264_nvenc @ 0x555b20edf980] Starting thread...
[vf#0:0 @ 0x555b20efc540] Starting thread...
[vist#0:0/rawvideo @ 0x555b20ede5c0] [dec:rawvideo @ 0x555b20efe100] Starting thread...
[in#0/rawvideo @ 0x555b20ecbd00] Starting thread...
Press [q] to stop, [?] for help
[in#0/rawvideo @ 0x555b20ecbd00] Error during demuxing: Transport endpoint is not connected
[in#0/rawvideo @ 0x555b20ecbd00] Terminating thread with return code 0 (success)
[vist#0:0/rawvideo @ 0x555b20ede5c0] [dec:rawvideo @ 0x555b20efe100] Decoder thread received EOF packet
[vist#0:0/rawvideo @ 0x555b20ede5c0] [dec:rawvideo @ 0x555b20efe100] Decoder returned EOF, finishing
[vist#0:0/rawvideo @ 0x555b20ede5c0] [dec:rawvideo @ 0x555b20efe100] Terminating thread with return code 0 (success)
detected 40 logical cores
[graph 0 input from stream 0:0 @ 0x7f6a4c003900] Setting 'video_size' to value '1920x1080'
[graph 0 input from stream 0:0 @ 0x7f6a4c003900] Setting 'pix_fmt' to value '0'
[graph 0 input from stream 0:0 @ 0x7f6a4c003900] Setting 'time_base' to value '1/25'
[graph 0 input from stream 0:0 @ 0x7f6a4c003900] Setting 'pixel_aspect' to value '0/1'
[graph 0 input from stream 0:0 @ 0x7f6a4c003900] Setting 'colorspace' to value '2'
[graph 0 input from stream 0:0 @ 0x7f6a4c003900] Setting 'range' to value '0'
[graph 0 input from stream 0:0 @ 0x7f6a4c003900] Setting 'frame_rate' to value '25/1'
[graph 0 input from stream 0:0 @ 0x7f6a4c003900] w:1920 h:1080 pixfmt:yuv420p tb:1/25 fr:25/1 sar:0/1 csp:unknown range:unknown
[format @ 0x7f6a4c005340] Setting 'pix_fmts' to value 'yuv420p'
[AVFilterGraph @ 0x7f6a4c000fc0] query_formats: 4 queried, 9 merged, 0 already done, 0 delayed
[out_0_0 @ 0x7f6a4c005040] EOF on sink link out_0_0:default.
[vf#0:0 @ 0x555b20efc540] Filtergraph returned EOF, finishing
[vf#0:0 @ 0x555b20efc540] All consumers returned EOF
[vost#0:0/h264_nvenc @ 0x555b20edf980] No filtered frames for output stream, trying to initialize anyway.
[h264_nvenc @ 0x555b20edfec0] Loaded lib: libcuda.so.1
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuInit
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDriverGetVersion
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGetCount
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGet
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGetAttribute
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGetName
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceComputeCapability
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuCtxCreate_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuCtxGetCurrent
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuCtxSetLimit
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuCtxPushCurrent_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuCtxPopCurrent_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuCtxDestroy_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemAlloc_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemAllocPitch_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemAllocManaged
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemsetD8Async
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemFree_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpy
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpyAsync
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpy2D_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpy2DAsync_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpyHtoD_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpyHtoDAsync_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpyDtoH_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpyDtoHAsync_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpyDtoD_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMemcpyDtoDAsync_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGetErrorName
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGetErrorString
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuCtxGetDevice
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDevicePrimaryCtxRetain
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDevicePrimaryCtxRelease
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDevicePrimaryCtxSetFlags
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDevicePrimaryCtxGetState
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDevicePrimaryCtxReset
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuStreamCreate
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuStreamQuery
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuStreamSynchronize
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuStreamDestroy_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuStreamAddCallback
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuStreamWaitEvent
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEventCreate
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEventDestroy_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEventSynchronize
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEventQuery
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEventRecord
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuLaunchKernel
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuLinkCreate
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuLinkAddData
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuLinkComplete
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuLinkDestroy
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuModuleLoadData
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuModuleUnload
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuModuleGetFunction
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuModuleGetGlobal
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuTexObjectCreate
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuTexObjectDestroy
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGLGetDevices_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGraphicsGLRegisterImage
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGraphicsUnregisterResource
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGraphicsMapResources
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGraphicsUnmapResources
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGraphicsSubResourceGetMappedArray
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuGraphicsResourceGetMappedPointer_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGetUuid
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGetUuid_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGetLuid
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGetByPCIBusId
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDeviceGetPCIBusId
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuImportExternalMemory
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDestroyExternalMemory
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuExternalMemoryGetMappedBuffer
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuExternalMemoryGetMappedMipmappedArray
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMipmappedArrayGetLevel
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuMipmappedArrayDestroy
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuImportExternalSemaphore
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuDestroyExternalSemaphore
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuSignalExternalSemaphoresAsync
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuWaitExternalSemaphoresAsync
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuArrayCreate_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuArray3DCreate_v2
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuArrayDestroy
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEGLStreamProducerConnect
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEGLStreamProducerDisconnect
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEGLStreamConsumerDisconnect
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEGLStreamProducerPresentFrame
[h264_nvenc @ 0x555b20edfec0] Loaded sym: cuEGLStreamProducerReturnFrame
[h264_nvenc @ 0x555b20edfec0] Loaded lib: libnvidia-encode.so.1
[h264_nvenc @ 0x555b20edfec0] Loaded sym: NvEncodeAPICreateInstance
[h264_nvenc @ 0x555b20edfec0] Loaded sym: NvEncodeAPIGetMaxSupportedVersion
[h264_nvenc @ 0x555b20edfec0] Loaded Nvenc version 12.2
[h264_nvenc @ 0x555b20edfec0] Nvenc initialized successfully
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuInit(0)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuDeviceGetCount(&nb_devices)
[h264_nvenc @ 0x555b20edfec0] 2 CUDA capable devices found
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuDeviceGet(&cu_device, idx)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuDeviceGetName(name, sizeof(name), cu_device)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuDeviceComputeCapability(&major, &minor, cu_device)
[h264_nvenc @ 0x555b20edfec0] [ GPU #0 - < Quadro P2000 > has Compute SM 6.1 ]
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxCreate(&ctx->cu_context_internal, 0, cu_device)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPopCurrent(&dummy)
[h264_nvenc @ 0x555b20edfec0] supports NVENC
[h264_nvenc @ 0x555b20edfec0] CQ(7680) mode enabled.
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPushCurrent(ctx->cu_context)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPopCurrent(&dummy)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPushCurrent(ctx->cu_context)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPopCurrent(&dummy)
Output #0, flv, to 'rtmp://127.0.0.1:1935/temp/qqq':
  Metadata:
    encoder         : Lavf61.1.100
  Stream #0:0, 0, 1/1000: Video: h264 (Main), 1 reference frame ([7][0][0][0] / 0x0007), yuv420p(progressive), 1920x1080, 0/1, q=2-31, 25 fps, 1k tbn
      Metadata:
        encoder         : Lavc61.3.100 h264_nvenc
      Side data:
        cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
[out#0/flv @ 0x555b20edecc0] Starting thread...
[vost#0:0/h264_nvenc @ 0x555b20edf980] Encoder thread received EOF
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPushCurrent(ctx->cu_context)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPopCurrent(&dummy)
[vost#0:0/h264_nvenc @ 0x555b20edf980] Terminating thread with return code 0 (success)
[vf#0:0 @ 0x555b20efc540] Terminating thread with return code 0 (success)
[out#0/flv @ 0x555b20edecc0] All streams finished
[out#0/flv @ 0x555b20edecc0] Terminating thread with return code 0 (success)
[flv @ 0x555b20edee00] Failed to update header with correct duration.
[flv @ 0x555b20edee00] Failed to update header with correct filesize.
[AVIOContext @ 0x555b20f01140] Statistics: 303 bytes written, 0 seeks, 2 writeouts
[rtmp @ 0x555b20f00240] UnPublishing stream...
[rtmp @ 0x555b20f00240] Deleting stream...
[out#0/flv @ 0x555b20edecc0] Output file #0 (rtmp://127.0.0.1:1935/temp/qqq):
[out#0/flv @ 0x555b20edecc0]   Output stream #0:0 (video): 0 frames encoded; 0 packets muxed (0 bytes);
[out#0/flv @ 0x555b20edecc0]   Total: 0 packets (0 bytes) muxed
[out#0/flv @ 0x555b20edecc0] video:0KiB audio:0KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: unknown
[out#0/flv @ 0x555b20edecc0] Output file is empty, nothing was encoded(check -ss / -t / -frames parameters if used)
frame=    0 fps=0.0 q=0.0 Lsize=       0KiB time=N/A bitrate=N/A speed=N/A
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPushCurrent(ctx->cu_context)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxPopCurrent(&dummy)
[h264_nvenc @ 0x555b20edfec0] Calling dl_fn->cuda_dl->cuCtxDestroy(ctx->cu_context_internal)
[h264_nvenc @ 0x555b20edfec0] Nvenc unloaded
[in#0/rawvideo @ 0x555b20ecbd00] Input file #0 (tcp://127.0.0.1:19010?listen=2):
[in#0/rawvideo @ 0x555b20ecbd00]   Input stream #0:0 (video): 0 packets read (0 bytes); 0 frames decoded; 0 decode errors;
[in#0/rawvideo @ 0x555b20ecbd00]   Total: 0 packets (0 bytes) demuxed
[AVIOContext @ 0x555b20edcd80] Statistics: 0 bytes read, 0 seeks

ffmpeg client:

 ./ffmpeg \
> -v 9 \
> -loglevel 99 \
> -f decklink \
> -format_code Hp25 \
> -i 'DeckLink Quad (1)' \
> -pix_fmt yuv420p \
> -r 25 \
> -f rawvideo \
> tcp://127.0.0.1:19010?tcp_nodelay=1
ffmpeg version n7.0.2 Copyright (c) 2000-2024 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: --pkg-config-flags=--static --extra-cflags=-I/usr/include/DeckLink --extra-libs='-lpthread -lm -ldl' --ld=g++ --enable-gpl --enable-nonfree --enable-pthreads --enable-avfilter --enable-libx264 --enable-nvenc --enable-decklink --enable-ffplay --enable-libzmq --enable-gnutls --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265
  libavutil      59.  8.100 / 59.  8.100
  libavcodec     61.  3.100 / 61.  3.100
  libavformat    61.  1.100 / 61.  1.100
  libavdevice    61.  1.100 / 61.  1.100
  libavfilter    10.  1.100 / 10.  1.100
  libswscale      8.  1.100 /  8.  1.100
  libswresample   5.  1.100 /  5.  1.100
  libpostproc    58.  1.100 / 58.  1.100
Splitting the commandline.
Reading option '-v' ... matched as option 'v' (set logging level) with argument '9'.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument '99'.
Reading option '-f' ... matched as option 'f' (force container format (auto-detected otherwise)) with argument 'decklink'.
Reading option '-format_code' ... matched as AVOption 'format_code' with argument 'Hp25'.
Reading option '-i' ... matched as input url with argument 'DeckLink Quad (1)'.
Reading option '-pix_fmt' ... matched as option 'pix_fmt' (set pixel format) with argument 'yuv420p'.
Reading option '-r' ... matched as option 'r' (override input framerate/convert to given output framerate (Hz value, fraction or abbreviation)) with argument '25'.
Reading option '-f' ... matched as option 'f' (force container format (auto-detected otherwise)) with argument 'rawvideo'.
Reading option 'tcp://127.0.0.1:19010?tcp_nodelay=1' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option v (set logging level) with argument 9.
Successfully parsed a group of options.
Parsing a group of options: input url DeckLink Quad (1).
Applying option f (force container format (auto-detected otherwise)) with argument decklink.
Successfully parsed a group of options.
Opening an input file: DeckLink Quad (1).
[decklink @ 0x55e3e8fcff40] Trying to find mode for frame size 0x0, frame timing 0/0, field order 0, direction 0, format code Hp25
[decklink @ 0x55e3e8fcff40] Found Decklink mode 1920 x 1080 with rate 25.00
[decklink @ 0x55e3e8fcff40] Using 2 input audio channels
[decklink @ 0x55e3e8fcff40] Frame received (#1) - No input signal detected - Frames dropped 1
[decklink @ 0x55e3e8fcff40] Probe buffer size limit of 5000000 bytes reached
[decklink @ 0x55e3e8fcff40] stream 0: start_time: 0 duration: NOPTS
[decklink @ 0x55e3e8fcff40] stream 1: start_time: 0 duration: NOPTS
[decklink @ 0x55e3e8fcff40] format: start_time: 0 duration: NOPTS (estimate from bit rate) bitrate=830976 kb/s
[aist#0:0/pcm_s16le @ 0x55e3e8fef240] Guessed Channel Layout: stereo
Input #0, decklink, from 'DeckLink Quad (1)':
  Duration: N/A, start: 0.000000, bitrate: 830976 kb/s
  Stream #0:0, 1, 1/1000000: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
  Stream #0:1, 2, 1/1000000: Video: rawvideo, 1 reference frame (UYVY / 0x59565955), uyvy422(progressive), 1920x1080, 0/1, 829440 kb/s, 25 tbr, 1000k tbn
Successfully opened the file.
Parsing a group of options: output url tcp://127.0.0.1:19010?tcp_nodelay=1.
Applying option pix_fmt (set pixel format) with argument yuv420p.
Applying option r (override input framerate/convert to given output framerate (Hz value, fraction or abbreviation)) with argument 25.
Applying option f (force container format (auto-detected otherwise)) with argument rawvideo.
Successfully parsed a group of options.
Opening an output file: tcp://127.0.0.1:19010?tcp_nodelay=1.
[out#0/rawvideo @ 0x55e3e8ff5040] No explicit maps, mapping streams automatically...
[vost#0:0/rawvideo @ 0x55e3e8ff5a80] Created video stream from input stream 0:1
[tcp @ 0x55e3e901a780] No default whitelist set
[tcp @ 0x55e3e901a780] Original list of addresses:
[tcp @ 0x55e3e901a780] Address 127.0.0.1 port 19010
[tcp @ 0x55e3e901a780] Interleaved list of addresses:
[tcp @ 0x55e3e901a780] Address 127.0.0.1 port 19010
[tcp @ 0x55e3e901a780] Starting connection attempt to 127.0.0.1 port 19010
[tcp @ 0x55e3e901a780] Successfully connected to 127.0.0.1 port 19010
Successfully opened the file.
Stream mapping:
  Stream #0:1 -> #0:0 (rawvideo (native) -> rawvideo (native))
[vost#0:0/rawvideo @ 0x55e3e8ff5a80] Starting thread...
[vf#0:0 @ 0x55e3e8ff0c80] Starting thread...
[vist#0:1/rawvideo @ 0x55e3e8ff4580] [dec:rawvideo @ 0x55e3e8ff28c0] Starting thread...
[in#0/decklink @ 0x55e3e8fcfbc0] Starting thread...
Press [q] to stop, [?] for help
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
    Last message repeated 1 times
detected 40 logical cores
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] Setting 'video_size' to value '1920x1080'
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] Setting 'pix_fmt' to value '15'
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] Setting 'time_base' to value '1/1000000'
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] Setting 'pixel_aspect' to value '0/1'
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] Setting 'colorspace' to value '2'
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] Setting 'range' to value '0'
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] Setting 'frame_rate' to value '25000/1000'
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] w:1920 h:1080 pixfmt:uyvy422 tb:1/1000000 fr:25000/1000 sar:0/1 csp:unknown range:unknown
[format @ 0x7f89a0005500] Setting 'pix_fmts' to value 'yuv420p'
[auto_scale_0 @ 0x7f89a00070c0] w:iw h:ih flags:'' interl:0
[format @ 0x7f89a0005500] auto-inserting filter 'auto_scale_0' between the filter 'Parsed_null_0' and the filter 'format'
[AVFilterGraph @ 0x7f89a00011c0] query_formats: 4 queried, 6 merged, 3 already done, 0 delayed
[auto_scale_0 @ 0x7f89a00070c0] w:1920 h:1080 fmt:uyvy422 csp:unknown range:unknown sar:0/1 -> w:1920 h:1080 fmt:yuv420p csp:unknown range:unknown sar:0/1 flags:0x00000004
[graph 0 input from stream 0:1 @ 0x7f89a0003b40] video frame properties congruent with link at pts_time: 0
Output #0, rawvideo, to 'tcp://127.0.0.1:19010?tcp_nodelay=1':
  Metadata:
    encoder         : Lavf61.1.100
  Stream #0:0, 0, 1/25: Video: rawvideo, 1 reference frame (I420 / 0x30323449), yuv420p(progressive), 1920x1080, 0/1, q=2-31, 622080 kb/s, 25 fps, 25 tbn
      Metadata:
        encoder         : Lavc61.3.100 rawvideo
[out#0/rawvideo @ 0x55e3e8ff5040] Starting thread...
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
    Last message repeated 9 times
[decklink @ 0x55e3e8fcff40] Frame received (#13) - Input returned - Frames dropped 2peed=0.72x
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[rawvideo @ 0x55e3e90192c0] PACKET SIZE: 4147200, STRIDE: 3840
[vost#0:0/rawvideo @ 0x55e3e8ff5a80] Error submitting a packet to the muxer: Connection reset by peer
    Last message repeated 1 times
[out#0/rawvideo @ 0x55e3e8ff5040] Error muxing a packet
[out#0/rawvideo @ 0x55e3e8ff5040] Task finished with error code: -104 (Connection reset by peer)
[out#0/rawvideo @ 0x55e3e8ff5040] Terminating thread with return code -104 (Connection reset by peer)
[decklink @ 0x55e3e8fcff40] Unknown meta data DID = 0x51 SDID = 0x52
[in#0/decklink @ 0x55e3e8fcfbc0] Terminating thread with return code 0 (success)
[vist#0:1/rawvideo @ 0x55e3e8ff4580] [dec:rawvideo @ 0x55e3e8ff28c0] Decoder thread received EOF packet
[vist#0:1/rawvideo @ 0x55e3e8ff4580] [dec:rawvideo @ 0x55e3e8ff28c0] Decoder returned EOF, finishing
[vist#0:1/rawvideo @ 0x55e3e8ff4580] [dec:rawvideo @ 0x55e3e8ff28c0] Terminating thread with return code 0 (success)
[out_0_0 @ 0x7f89a00051c0] EOF on sink link out_0_0:default.
[vf#0:0 @ 0x55e3e8ff0c80] Filtergraph returned EOF, finishing
[vf#0:0 @ 0x55e3e8ff0c80] All consumers returned EOF
[vost#0:0/rawvideo @ 0x55e3e8ff5a80] Encoder thread received EOF
[vost#0:0/rawvideo @ 0x55e3e8ff5a80] Terminating thread with return code 0 (success)
[vf#0:0 @ 0x55e3e8ff0c80] Terminating thread with return code 0 (success)
[out#0/rawvideo @ 0x55e3e8ff5040] Error writing trailer: Connection reset by peer
[AVIOContext @ 0x55e3e8fef640] Statistics: 1769472 bytes written, 0 seeks, 95 writeouts
[out#0/rawvideo @ 0x55e3e8ff5040] Error closing file: Connection reset by peer
[out#0/rawvideo @ 0x55e3e8ff5040] Output file #0 (tcp://127.0.0.1:19010?tcp_nodelay=1):
[out#0/rawvideo @ 0x55e3e8ff5040]   Output stream #0:0 (video): 21 frames encoded; 1 packets muxed (3110400 bytes);
[out#0/rawvideo @ 0x55e3e8ff5040]   Total: 1 packets (3110400 bytes) muxed
[out#0/rawvideo @ 0x55e3e8ff5040] video:3038KiB audio:0KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: unknown
frame=    1 fps=0.0 q=-0.0 Lsize=    1728KiB time=00:00:00.36 bitrate=39321.6kbits/s speed=0.445x
[in#0/decklink @ 0x55e3e8fcfbc0] Input file #0 (DeckLink Quad (1)):
[in#0/decklink @ 0x55e3e8fcfbc0]   Input stream #0:1 (video): 22 packets read (91238400 bytes); 21 frames decoded; 0 decode errors;
[in#0/decklink @ 0x55e3e8fcfbc0]   Total: 22 packets (91238400 bytes) demuxed
Conversion failed!

Sufficient information

• The same command using *single client* mode (listen=1) works fine.
• I tested in ffmpeg versions n7.0.2 and n4.4. They behave the same way.
• When two tcp inputs are in use, the ffmpeg does NOT start listening the second input until the first input establishes connection. So it is impossible for ffmpeg client to connect to the second input of the ffmpeg server.