Помогите разобраться с sendto

int send_sres(uint8_t *rand, char *imsi, uint8_t *sres)
{

	//const char* cmdPath = DEFAULT_CMD_PATH;

	//char rspPath[200];
	//sprintf(rspPath,"/tmp/OpenBTS.console.%d.%8lx",getpid(),time(NULL));


	//printf("command socket path is %s\n", cmdPath);


	// the socket
	int sock = socket(AF_INET,SOCK_DGRAM,0);
	if (sock<0) {
		perror("opening datagram socket");
		exit(1);
	}
	FILE *bts_addr;
	bts_addr = fopen(DEFAULT_BTS_ADDR,"r");
	if(bts_addr == NULL)
		perror("Error while loading bts_addr file\n");
	char *inaddr=NULL;
	size_t inaddr_len=0;
	getline(&inaddr,&inaddr_len,bts_addr);
	fclose(bts_addr);
	// destination address
	struct sockaddr_in cmdSockName;
	memset(&cmdSockName, 0, sizeof(struct sockaddr_in));
	cmdSockName.sin_family = AF_INET;
   	cmdSockName.sin_addr.s_addr = inet_addr(inaddr);
   	printf("Server addr %s\n", inaddr); 
   	cmdSockName.sin_port = htons(5065); 
	

	// locally bound address
	struct sockaddr_in rspSockName;
	memset(&rspSockName, 0, sizeof(struct sockaddr_in));
	rspSockName.sin_family = AF_INET;
	rspSockName.sin_addr.s_addr = inet_addr("127.0.0.1");
	rspSockName.sin_port=htons(5066);
	
	if (bind(sock, (struct sockaddr *) &rspSockName, sizeof(struct sockaddr_in))) {
		perror("binding name to datagram socket");
		free(inaddr);
		exit(1);
	}
	

		char *randc;  //fgets(inbuf,199,stdin);
		//char *cmd; 
		char buf[128];

		randc=osmo_hexdump_nospc(rand,16);

		 strcat(strcat(strcat(strcpy(buf, "getsres "), imsi), " "), randc);
		 printf("rand : %s\n",buf);


	

		// use the socket
		if (sendto(sock, buf, sizeof(buf),0,(struct sockaddr*)&cmdSockName,sizeof(struct sockaddr))<0) {
			perror("sending datagram");
			printf("Error sent to socket\n");
		}
		else{
			printf("We successfully sended rand\n");	
		}

		const int bufsz = 100000;
		char resbuf[bufsz];
		int nread = recv(sock,resbuf,bufsz-1,0);
		if (nread<0) {
			perror("receiving response");
		}
		resbuf[nread] = '\0';
		printf("%s\n",resbuf);
		if (nread==(bufsz-1)) printf("(response truncated at %d characters)\n",nread);
	 	osmo_hexparse(resbuf,sres,4);
	free(inaddr);	
	close(sock);

}

rand : getsres 250016387796246 89eef4f1949bb3d686fc49179d415847
sending datagram: Invalid argument
Error sent to socket