Tutorial: client and server

The two ends differ only at open and accept. A server opens with netchan_open(1) and, on the first datagram from a new peer, calls netchan_accept() to complete the handshake. A server that talks to many clients keeps one struct netchan_conn per peer, routing an incoming datagram to the right one; netchan_peek_id() reads the connection id out of a raw packet without parsing it, which is how a dispatcher picks the connection before feeding the bytes in.

A channel carries a content type set when it opens, and the peer reads it back with netchan_chan_content_type(). Use it to tell channels apart when one connection carries several. A server that offers a “chat” channel and a “presence” channel decides which handler a datagram belongs to from that string, before it looks at the payload.

case NETCHAN_EV_CHAN_OPEN:
    if (strcmp(netchan_chan_content_type(ev.ch), "chat") == 0)
        peer->chat = ev.ch;
    break;

One caution the examples learned the hard way: do not free a connection from inside its own poll loop. Handling NETCHAN_EV_DISCONNECTED by calling netchan_close() and then looping back to netchan_poll() reads a freed pointer. Note that the slot is gone and break out of the loop first.