/* NAME client.go DESCRIPTION client.go provides an RTP client. AUTHOR Saxon A. Nelson-Milton <saxon@ausocean.org> LICENSE This is Copyright (C) 2019 the Australian Ocean Lab (AusOcean). It is free software: you can redistribute it and/or modify them under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. It is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License in gpl.txt. If not, see http://www.gnu.org/licenses. */ package rtp import ( "net" "sync" ) // Client describes an RTP client that can receive an RTP stream and implements // io.Reader. type Client struct { r *PacketReader ssrc uint32 mu sync.Mutex sequence uint16 cycles uint16 } // NewClient returns a pointer to a new Client. // // addr is the address of form <ip>:<port> that we expect to receive // RTP at. func NewClient(addr string) (*Client, error) { c := &Client{r: &PacketReader{}} a, err := net.ResolveUDPAddr("udp", addr) if err != nil { return nil, err } c.r.PacketConn, err = net.ListenUDP("udp", a) if err != nil { return nil, err } return c, nil } // SSRC returns the identified for the source from which the RTP packets being // received are coming from. func (c *Client) SSRC() uint32 { return c.ssrc } // Read implements io.Reader. func (c *Client) Read(p []byte) (int, error) { n, err := c.r.Read(p) if err != nil { return n, err } if c.ssrc == 0 { c.ssrc, _ = SSRC(p[:n]) } s, _ := Sequence(p[:n]) c.setSequence(s) return n, err } // setSequence sets the most recently received sequence number, and updates the // cycles count if the sequence number has rolled over. func (c *Client) setSequence(s uint16) { c.mu.Lock() if s < c.sequence { c.cycles++ } c.sequence = s c.mu.Unlock() } // Sequence returns the most recent RTP packet sequence number received. func (c *Client) Sequence() uint16 { c.mu.Lock() defer c.mu.Unlock() return c.sequence } // Cycles returns the number of RTP sequence number cycles that have been received. func (c *Client) Cycles() uint16 { c.mu.Lock() defer c.mu.Unlock() return c.cycles } // PacketReader provides an io.Reader interface to an underlying UDP PacketConn. type PacketReader struct { net.PacketConn } // Read implements io.Reader. func (r PacketReader) Read(b []byte) (int, error) { n, _, err := r.PacketConn.ReadFrom(b) return n, err }