echo-server-ipv6.c

#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define MAX_ENAME 133
#define BUF_SIZE 254
#define PORT_NUM 5055

static char *ename[] = {
    /*   0 */ "", 
    /*   1 */ "EPERM", "ENOENT", "ESRCH", "EINTR", "EIO", "ENXIO", 
    /*   7 */ "E2BIG", "ENOEXEC", "EBADF", "ECHILD", 
    /*  11 */ "EAGAIN/EWOULDBLOCK", "ENOMEM", "EACCES", "EFAULT", 
    /*  15 */ "ENOTBLK", "EBUSY", "EEXIST", "EXDEV", "ENODEV", 
    /*  20 */ "ENOTDIR", "EISDIR", "EINVAL", "ENFILE", "EMFILE", 
    /*  25 */ "ENOTTY", "ETXTBSY", "EFBIG", "ENOSPC", "ESPIPE", 
    /*  30 */ "EROFS", "EMLINK", "EPIPE", "EDOM", "ERANGE", 
    /*  35 */ "EDEADLK/EDEADLOCK", "ENAMETOOLONG", "ENOLCK", "ENOSYS", 
    /*  39 */ "ENOTEMPTY", "ELOOP", "", "ENOMSG", "EIDRM", "ECHRNG", 
    /*  45 */ "EL2NSYNC", "EL3HLT", "EL3RST", "ELNRNG", "EUNATCH", 
    /*  50 */ "ENOCSI", "EL2HLT", "EBADE", "EBADR", "EXFULL", "ENOANO", 
    /*  56 */ "EBADRQC", "EBADSLT", "", "EBFONT", "ENOSTR", "ENODATA", 
    /*  62 */ "ETIME", "ENOSR", "ENONET", "ENOPKG", "EREMOTE", 
    /*  67 */ "ENOLINK", "EADV", "ESRMNT", "ECOMM", "EPROTO", 
    /*  72 */ "EMULTIHOP", "EDOTDOT", "EBADMSG", "EOVERFLOW", 
    /*  76 */ "ENOTUNIQ", "EBADFD", "EREMCHG", "ELIBACC", "ELIBBAD", 
    /*  81 */ "ELIBSCN", "ELIBMAX", "ELIBEXEC", "EILSEQ", "ERESTART", 
    /*  86 */ "ESTRPIPE", "EUSERS", "ENOTSOCK", "EDESTADDRREQ", 
    /*  90 */ "EMSGSIZE", "EPROTOTYPE", "ENOPROTOOPT", 
    /*  93 */ "EPROTONOSUPPORT", "ESOCKTNOSUPPORT", 
    /*  95 */ "EOPNOTSUPP/ENOTSUP", "EPFNOSUPPORT", "EAFNOSUPPORT", 
    /*  98 */ "EADDRINUSE", "EADDRNOTAVAIL", "ENETDOWN", "ENETUNREACH", 
    /* 102 */ "ENETRESET", "ECONNABORTED", "ECONNRESET", "ENOBUFS", 
    /* 106 */ "EISCONN", "ENOTCONN", "ESHUTDOWN", "ETOOMANYREFS", 
    /* 110 */ "ETIMEDOUT", "ECONNREFUSED", "EHOSTDOWN", "EHOSTUNREACH", 
    /* 114 */ "EALREADY", "EINPROGRESS", "ESTALE", "EUCLEAN", 
    /* 118 */ "ENOTNAM", "ENAVAIL", "EISNAM", "EREMOTEIO", "EDQUOT", 
    /* 123 */ "ENOMEDIUM", "EMEDIUMTYPE", "ECANCELED", "ENOKEY", 
    /* 127 */ "EKEYEXPIRED", "EKEYREVOKED", "EKEYREJECTED", 
    /* 130 */ "EOWNERDEAD", "ENOTRECOVERABLE", "ERFKILL", "EHWPOISON"
};

void errExit(char message[]) {
	// errExit
	// prints error text corresponding to errno
	// plus error description as returned by strerror()
	// also terminate program by calling exit()
	// TODO(yudhi): Add EF_DUMPCORE and learn about dumpfiles
	
	int savederrno = errno;
	char errText[BUF_SIZE];

	snprintf(errText, BUF_SIZE, "[%s %s]", 
	(savederrno > 0 && savederrno < MAX_ENAME) ?
	ename[savederrno]: "?UNKNOWN?", strerror(savederrno));
	puts(message);
	puts(errText);
	exit(EXIT_FAILURE);
}

int main(void) {
	struct sockaddr_in6 serverAddr, clientAddr;
	int socketDescriptor;
	ssize_t numBytes;
	socklen_t len;
	char buf[BUF_SIZE];
	char clientAddrStr[INET6_ADDRSTRLEN];

	socketDescriptor = socket(AF_INET6, SOCK_DGRAM, 0);
	if (socketDescriptor == -1) {
		errExit("Socket");
	}

	memset(&serverAddr, 0, sizeof(serverAddr));
	serverAddr.sin6_family = AF_INET6;
	// Wildcard Address
	serverAddr.sin6_addr = in6addr_any;
	serverAddr.sin6_port = htons(PORT_NUM);

	if (bind(socketDescriptor, (struct sockaddr *) &serverAddr, sizeof(struct sockaddr_in6)) == -1) {
		errExit("Bind");
	}

	for(;;) {
		len = sizeof(struct sockaddr_in6);
		numBytes = recvfrom(socketDescriptor, buf, BUF_SIZE, 0, (struct sockaddr *) &clientAddr, &len);

		if (numBytes == -1) {
			errExit("recvFrom");
		}

		if (inet_ntop(AF_INET6, &clientAddr.sin6_addr, clientAddrStr, INET6_ADDRSTRLEN) == NULL) {
			printf("Couldn't convert client address to string\n");
		} else {
			printf("Server received %ld bytes from (%s %u)\n", (long) numBytes, clientAddrStr, ntohs(clientAddr.sin6_port));
		}
		if (sendto(socketDescriptor, buf, numBytes, 0, (struct sockaddr *) &clientAddr, len) != numBytes) {
			puts("sendTo");
			exit(EXIT_FAILURE);
		}
	}

	return EXIT_SUCCESS;
}