libdill: Structured Concurrency for C

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NAME

udp_open_mem - opens an UDP socket

SYNOPSIS

#include <libdill.h>

int udp_open_mem(
    struct ipaddr* local,
    struct ipaddr* remote,
    struct udp_storage* mem);

DESCRIPTION

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.

This function allows to avoid one dynamic memory allocation by storing the object in user-supplied memory. Unless you are hyper-optimizing use udp_open instead.

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.

mem: The structure to store the newly created object in. It must not be deallocated before the object is closed.

To close this socket use hclose function.

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

RETURN VALUE

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.

ERRORS

• EADDRINUSE: The local address is already in use.
• EADDRNOTAVAIL: The specified address is not available from the local machine.
• EINVAL: Invalid argument.
• EMFILE: The maximum number of file descriptors in the process are already open.
• ENFILE: The maximum number of file descriptors in the system are already open.
• ENOMEM: Not enough memory.

EXAMPLE

struct ipaddr local;
ipaddr_local(&local, NULL, 5555, 0);
struct ipaddr remote;
ipaddr_remote(&remote, "server.example.org", 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(s);

SEE ALSO

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