int main(int argc, char** argv) {
if (argc != 2)
fatal(usage_msg);
unsigned short int tcp_port, udp_port;
unsigned int data_len;
int tcp_sock, msg_sock;
struct sockaddr_in server_address;
struct sockaddr_in client_address;
socklen_t client_address_len;
ssize_t tcp_rcv_len;
tcp_port = str_to_short(argv[1], usage_msg);
tcp_sock = socket(PF_INET, SOCK_STREAM, 0); // creating IPv4 TCP socket
if (tcp_sock <0)
syserr("socket");
server_address.sin_family = AF_INET; // IPv4
server_address.sin_addr.s_addr = htonl(INADDR_ANY); // listening on all interfaces
server_address.sin_port = htons(tcp_port); // listening on port from args
// bind the socket to a concrete address
if (bind(tcp_sock, (struct sockaddr *) &server_address, sizeof(server_address)) < 0)
syserr("bind");
// switch to listening (passive open)
if (listen(tcp_sock, QUEUE_LENGTH) < 0)
syserr("listen");
printf("Accepting client connections on port %hu\n", ntohs(server_address.sin_port));
for (;;) {
client_address_len = sizeof(client_address);
// get client connection from the socket
msg_sock = accept(tcp_sock, (struct sockaddr *) &client_address, &client_address_len);
if (msg_sock < 0)
syserr("accept");
//read port number
tcp_rcv_len = read(msg_sock, &udp_port, sizeof(udp_port));
udp_port = ntohs(udp_port);
if (tcp_rcv_len < 0)
syserr("Reading from client socket");
else if (tcp_rcv_len > 0) {
printf("Read port number from socket: %d\n", udp_port);
data_len = 0;
while (tcp_rcv_len > 0) {
tcp_rcv_len = read(msg_sock, buffer, sizeof(buffer));
data_len += tcp_rcv_len;
}
if (close(msg_sock) < 0)
syserr("close");
int sock;
ssize_t snd_len, rcva_len;
struct sockaddr_in my_address;
my_address.sin_family = AF_INET; // IPv4
my_address.sin_addr.s_addr =
client_address.sin_addr.s_addr; // address IP
my_address.sin_port = htons((uint16_t) udp_port);
sock = socket(PF_INET, SOCK_DGRAM, 0);
if (sock < 0)
syserr("socket");
printf("Sending to UDP socket: %u\n\n", data_len);
data_len = htonl(data_len);
rcva_len = (socklen_t) sizeof(my_address);
snd_len = sendto(sock, &data_len, sizeof(data_len), 0,
(struct sockaddr *) &my_address, rcva_len);
if (snd_len != sizeof(data_len)) {
syserr("partial / failed UDP write");
}
if (close(sock) == -1) { //very rare errors can occur here, but then
syserr("close"); //it's healthy to do the check
}
}
}
close(tcp_sock);
return 0;
}
int str_is_short(const char *string, const int base)
{
short number;
return str_to_short(string, &number, base);
}