Strange behaviour while sending broadcast message - c

Question

I have two programs: client and server. They're trying to find themselves in local network using broadcast.
Client sends simple packet on broadcast with SERVER_PORT (known before) and server prints info about connection, but when i tried this solution I found some strange behavaiour, when I uncomment last two lines of server.c server prints (one custom struct)
Connection from: 0.0.0.0 on port: 0
after commenting those lines everything works properly, am I missing something?
server.c
int broadcast_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
struct sockaddr_in broadcast_addr;
broadcast_addr.sin_addr.s_addr = INADDR_ANY;
broadcast_addr.sin_port = htons(SERVER_PORT);
broadcast_addr.sin_family = AF_INET;
if (bind(broadcast_socket, (struct sockaddr *)&broadcast_addr,
sizeof(broadcast_addr))) {
perror("bind");
}
struct sockaddr_in recv_addr;
char buf[MAX_PACKET_SIZE];
socklen_t len;
if (recvfrom(broadcast_socket, buf, MAX_PACKET_SIZE, 0,
(struct sockaddr *)&recv_addr, &len) < 0) {
perror("recvfrom");
}
printf("Connection from: %s on port: %d\nMessage: %s\n",
inet_ntoa(recv_addr.sin_addr), ntohs(recv_addr.sin_port), buf);
/* struct network_packet packet; */
/* struct sockaddr_in my_addr; */
client.c
int find_server(struct sockaddr_in *out) {
struct sockaddr_in broadcast;
struct network_packet packet;
int yes = 1;
socklen_t len;
broadcast.sin_addr.s_addr = INADDR_ANY;
broadcast.sin_port = htons(CLIENT_PORT);
broadcast.sin_family = AF_INET;
int socket_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (bind(socket_fd, (struct sockaddr *)&broadcast, sizeof(broadcast))) {
perror("bind");
}
if (get_broadcast_addr(&broadcast.sin_addr)) {
return -1;
}
printf("Target address: %s\n", inet_ntoa(broadcast.sin_addr));
broadcast.sin_port = htons(SERVER_PORT);
broadcast.sin_family = AF_INET;
setsockopt(socket_fd, SOL_SOCKET, SO_BROADCAST, &yes, sizeof(yes));
char buf[10] = "test";
sendto(socket_fd, buf, strlen(buf), 0, (struct sockaddr *)&broadcast,
sizeof(broadcast));
if (recvfrom(socket_fd, &packet, sizeof(packet), 0,
(struct sockaddr *)&broadcast, &len) < 0) {
perror("recvfrom");
}
struct sockaddr_in *sa = (struct sockaddr_in *)packet.data;
memcpy(out, sa, packet.header.packet_length);
return 0;
}
struct network_packet_header {
enum network_packet_type type;
int packet_length;
};
struct network_packet {
struct network_packet_header header;
unsigned char data[MAX_DATA_LENGTH];
};

Answer 1

You have to initialize the variable you pass as recvfrom's addrlen to the size of the address struct.