--- name: "udpxy" section: "1" platform: "linux" package: "udpxy" version: "1.0.25.1-2" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/udpxy" --- # udpxy(1) a UDP-to-HTTP multicast traffic relay daemon. ## NAME udpxy - a UDP-to-HTTP multicast traffic relay daemon. ## SYNOPSIS **udpxy** \[-vTS\] \[-a *\*\] \[-m *\*\] \[-c *\*\] \[-l *\*\] \[-B *\*\] \[-R *\*\] \[-H *\*\] \[-n *\*\] \[-M *\*\] -p *\* ## DESCRIPTION udpxy is a *UDP-to-HTTP multicast traffic relay daemon*: it forwards UDP traffic from a given multicast subscription to the requesting HTTP client. udpxy listens (on a dedicated address/port) for HTTP requests issued by clients. A client request should be structured as: http://{*address*}:{*port*}/{*cmd*}/{*mgroup\_address*}\[**SEP**\]{*mgroup\_port*} - **\[SEP\]** :\|%\|~\|+\|-\|^ - **{cmd}** udp\|rtp where *address* and *port* match the listening *address/port* combination of udpxy, and *mgroup\_address*:*mgroup\_port* identify the multicast group/channel to subscribe to. - **udp** *udp* command will have udpxy probe for known types of payload (such as *MPEG-TS* and *RTP over MPEG-TS*); - **rtp** *rtp* command makes udpxy assume *RTP over MPEG-TS* payload, thus skipping the probes. udpxy will start a separate *client process* for each new relay request (within the specified limit on active clients). The client process will relay/forward all network traffic received (via a UDP socket) from the specified multicast group to the requesting HTTP connection. udpxy also supports a few administrative requests: - **status** http://*address*:*port*/**status**/ to send back an HTML page with daemon status and client statistics. - **restart** http://*address*:*port*/**restart**/ to close all active connections and restart. ## EXAMPLES http://192.168.0.12:5056/udp/224.0.2.26:24012 http://192.168.0.12:5056/rtp/224.0.2.26:24012 http://192.168.0.15:5056/rtp/224.0.2.26^24055 http://192.168.0.15:5056/status/ ## OPTIONS udpxy accepts the following options: - **-v** Enable verbose output \[default = *disabled*\]. - **-S** Enable client statistics \[default = *disabled*\]. - **-T** Do NOT run as a daemon \[default = *daemon if root*\]. - **-a *\*** IPv4 address/interface to listen on \[default = *0.0.0.0*\]. - **-m *\*** IPv4 address/interface of (multicast) source \[default = *0.0.0.0*\]. - **-c *\*** Maximum number of clients to accept \[default = *3*, max = *5000*\]. - **-l *\*** Log output to file \[default = *stderr*\]. - **-B *\*** Buffer size (65536, 32Kb, 1Mb) for inbound (multicast) data \[default = *2048 bytes*\]. - **-R *\*** Maximum number of messages to buffer (*-1* = *all*) \[default = *1*\]. - **-H *\*** Maximum time (in seconds) to hold data in a buffer (*-1* = *unlimited*) \[default = *1*\]. - **-n *\*** Nice value increment \[default = *0*\]. - **-M *\*** Renew multicast subscription every M seconds (*skip* if *0*) \[default = *0*\]. - **-p *\*** Port to listen on. ## PAYLOAD TYPES AND HANDLING udpxy recognizes *MPEG-TS* and *RTP over MPEG-TS* payloads within relayed packets; if udpxy encounters RTP payload it automatically 'translates' it to MPEG-TS (by stripping RTP headers) so that media players not recognizing RTP could still play back the stream. So far, no translation is performed for other payload types. ## RECORDING MPEG TRAFFIC udpxy includes functionality to record captured traffic as *raw MPEG-TS stream* into a file. This functionality is enabled through **udpxrec**: a bundled-in application that is linked together with udpxy (as one executable). udpxrec is invoked via a symbolic link (named **udpxrec**) to the udpxy executable (i.e. **do not rename** udpxy executable). udpxrec creates MPEG files encapsulating MPEG-TS segments; certain media players will **NOT** play such files; in order to make them playable the stream must be transcoded to MPEG-PS; vlc 'knows' how to do such transcoding, here is a command-line example: **vlc input-ts.mpg --sout="#std{access=file,mux=ps,dst=out-ps.mpg}"** The resulting MPEG-PS file can be played back by most media players. ## ENVIRONMENT udpxy utilizes the following environment variables to compliment its command-line options; the variables are considered for the options that most people would not need to change too often (or simply inconvenient to use from the command line). **NB**: If there is a command-line switch that would intersect in functionality with an environment variable, the switch *always* has higher priority. - **UDPXY\_RCV\_TMOUT** timeout (sec) on the *inbound* data stream (*multicast*), default=*5*; - **UDPXY\_DHOLD\_TMOUT** timeout (sec) to hold buffered data before sending/flushing to client(s), default=*1*; - **UDPXY\_SREAD\_TMOUT** timeout (sec) to *read* from the listening socked (handling HTTP requests), default=*1*; - **UDPXY\_SWRITE\_TMOUT** timeout (sec) to *write* to the listening socked (handling HTTP requests), default=*1*; - **UDPXY\_SSEL\_TMOUT** timeout (sec) to *[select(2)](/select/2.md)* in server loop (unused if *[pselect(2)](/pselect/2.md)* is employed), default=*30*; - **UDPXY\_LQ\_BACKLOG** size of the listener socket's *backlog*, default=*16*; - **UDPXY\_SRV\_RLWMARK** low watermaek on the receiving (m-cast) socket, default=*0* (*not set*); - **UDPXY\_SSOCKBUF\_NOSYNC** do not sync *inbound* (UDP) socket's buffer size (with the value set by *-B*), default=*1* (*sync*); - **UDPXY\_DSOCKBUF\_NOSYNC** do not sync *outbound* (TCP) socket's buffer size (with the value set by *-B*), default=*1* (*sync*); - **UDPXY\_TCP\_NODELAY** disable *Nagle algorithm* on the newly accepted socket (faster channel switching), default=*1*; - **UDPXY\_HTTP200\_FTR\_FILE** append contents of the given text file to the *HTTP 200* response, default=*none*; - **UDPXY\_HTTP200\_FTR\_LN** append the text (line) to the *HTTP 200* response, default=*none*; - **UDPXY\_ALLOW\_PAUSES** if blocked on a *[write(2)](/write/2.md)*, keep reading data until the buffer (**-B** *\*) is full, default=*disabled*; - **UDPXY\_PAUSE\_MSEC** allow only *N* milliseconds of reading data when blocked on a *[write(2)](/write/2.md)*. - **UDPXY\_CONTENT\_TYPE** specify custom **Content-Type** in *HTTP* responses. ## AUTHORS Pavel V. Cherenkov and all the good people who submitted patches or otherwise contributed to the project. ## SEE ALSO [**udpxrec**(1)](/udpxrec/1.md)