libdill: Structured Concurrency for C


udp_open - opens an UDP socket


#include <libdill.h>

int udp_open(
    struct ipaddr* local,
    struct ipaddr* remote);


UDP is an unreliable message-based protocol defined in RFC 768. The size of the message is limited. The protocol has no initial or terminal handshake. A single socket can be used to different destinations.

This function creates an UDP socket.

local: IP address to be used to set source IP address in outgoing packets. Also, the socket will receive packets sent to this address. If port in the address is set to zero an ephemeral port will be chosen and filled into the local address.

remote: IP address used as default destination for outbound packets. It is used when destination address in udp_send function is set to NULL. It is also used by msend and mrecv functions which don't allow to specify the destination address explicitly. Furthermore, if remote address is set, all the packets arriving from different addresses will be silently dropped.

To close this socket use hclose function.

This function is not available if libdill is compiled with --disable-sockets option.


In case of success the function returns newly created socket handle. In case of error it returns -1 and sets errno to one of the values below.



struct ipaddr local;
ipaddr_local(&local, NULL, 5555, 0);
struct ipaddr remote;
ipaddr_remote(&remote, "", 5555, 0, -1);
int s = udp_open(&local, &remote);
udp_send(s1, NULL, "ABC", 3);
char buf[2000];
ssize_t sz = udp_recv(s, NULL, buf, sizeof(buf), -1);


hclose(3) mrecv(3) mrecvl(3) msend(3) msendl(3) udp_open_mem(3) udp_recv(3) udp_recvl(3) udp_send(3) udp_sendl(3)