send and receive simultaneously

values were ok, EDDB has a mag derivation of ~4° *facepalm*

.gitignore

@@ -0,0 +1 @@
+bin/

Makefile

@@ -1,9 +1,12 @@
 BIN=bin
 
-all: dirs command
+all: dirs command readref
 
-command: command.c
-	gcc -o ${BIN}/command command.c
+command:
+	gcc -o ${BIN}/command network.c command.c
+
+readref:
+	gcc -o ${BIN}/readref network.c readref.c
 
 .PHONY: clean dirs
 clean:

command.c

@@ -2,52 +2,10 @@
 #include <stdio.h>
 #include <string.h>
 
-#include <sys/socket.h>
-#include <sys/types.h> // BSD compatible
-#include <arpa/inet.h>
-#include <unistd.h>
-
-#include <errno.h>
-#include <netdb.h>
-
-#define SERVER "::1"
-#define PORT 49000
-
-#define COMMAND_BUFFER 256
-
-char* printable(char *str) {
-	char *ret = strdup(str);
-
-	for (int i = strlen(ret); i >= 0; i--) {
-		if (ret[i] == '\r' || ret[i] == '\n') {
-			ret[i] = '\0';
-		}
-	}
-
-	return ret;
-}
-
-void sendCommand(int sock, char *cmd) {
-	char bytesToSend[COMMAND_BUFFER];
-	memset(bytesToSend, 0, COMMAND_BUFFER);
-
-	strcpy(&bytesToSend[0], "CMND");
-	strcpy(&bytesToSend[5], cmd);
-
-	int numBytesSend = send(sock, bytesToSend, 5 + strlen(cmd), 0);
-	if (numBytesSend >= 0) {
-		//printf("Send %d bytes to %s:%d: %s\n", numBytesSend, SERVER, PORT, printable(bytesToSend));
-	} else {
-		fprintf(stderr, "Failed to send message to %s:%d (%d): %s", SERVER, PORT, errno, strerror(errno));
-		exit(EXIT_FAILURE);
-	}
-}
+#include "network.h"
 
 int main(int argc, char *argv[]) {
-	int xplaneSocket;
-	struct sockaddr_in6 xplaneAddress;
-
-	int err;
+	int xPlaneSocket;
 
 	// check argument
 	if (argc != 2) {
@@ -55,29 +13,18 @@ int main(int argc, char *argv[]) {
 		exit(EXIT_FAILURE);
 	}
 
-	// create socket
-	xplaneSocket = socket(AF_INET6, SOCK_DGRAM, 0);
-	if (xplaneSocket == -1) {
-		fprintf(stderr, "Error creating socket (%d): %s\n", errno, strerror(errno));
-		exit(EXIT_FAILURE);
-	}
-
-	// prepare address struct
-	xplaneAddress.sin6_family = AF_INET6;
-	xplaneAddress.sin6_port = htons(PORT);
-	inet_pton(AF_INET6, SERVER, &xplaneAddress.sin6_addr.s6_addr);
-
-	// connect to xplane
-	err = connect(xplaneSocket, (struct sockaddr *)&xplaneAddress, sizeof(xplaneAddress));
-	if (err) {
-		fprintf(stderr, "Error connecting %s:%d (%d): %s\n", SERVER, PORT, err, gai_strerror(err));
+	// network
+	xPlaneSocket = createSocket(SRC_PORT);
+	if (xPlaneSocket < 0) {
 		exit(EXIT_FAILURE);
 	}
 
 	// send payload
-	sendCommand(xplaneSocket, argv[1]);
+	if (sendToXPlane(xPlaneSocket, DEST_SERVER, DEST_PORT, "CMND", argv[1], strlen(argv[1])) < 0) {
+		exit(EXIT_FAILURE);
+	}
 
 	// bye bye (and no, I don't care about error anymore; I'll exit anyway?!)
-	close(xplaneSocket);
+	closeSocket(xPlaneSocket);
 	exit(EXIT_SUCCESS);
 }

network.c

@@ -0,0 +1,100 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <sys/socket.h>
+#include <sys/types.h> // BSD compatible
+#include <arpa/inet.h>
+#include <unistd.h>
+
+#include <errno.h>
+#include <netdb.h>
+
+#include "network.h"
+
+const int DGRAM_MSG_START = 0;
+const int DGRAM_PAYLOAD_START = DGRAM_MSG_START + DGRAM_MSG_LENGTH + DGRAM_NULL_LENGTH;
+
+int sendToXPlane(int sock, char *destAddr, int destPort, char *msg, void *payload, int lengthOfPayload) {
+	char bytesToSend[SEND_BUFFER];
+	struct sockaddr_in6 xPlaneAddress;
+	memset(bytesToSend, 0, SEND_BUFFER);
+
+	// msg is always 4 bytes long
+	if (strlen(msg) != DGRAM_MSG_LENGTH) {
+		return -10;
+	}
+
+	// payload shouldn't exceed buffer
+	if (lengthOfPayload > (SEND_BUFFER - DGRAM_MSG_LENGTH - DGRAM_NULL_LENGTH)) {
+		return -11;
+	}
+
+	strcpy(&bytesToSend[DGRAM_MSG_START], msg);
+	memcpy(&bytesToSend[DGRAM_PAYLOAD_START], payload, lengthOfPayload);
+
+	// prepare destination address struct
+	xPlaneAddress.sin6_family = AF_INET6;
+	xPlaneAddress.sin6_port = htons(destPort);
+	inet_pton(AF_INET6, destAddr, &xPlaneAddress.sin6_addr.s6_addr);
+
+	int numBytesSend = sendto(sock, bytesToSend, DGRAM_MSG_LENGTH + DGRAM_NULL_LENGTH + lengthOfPayload, 0, (struct sockaddr *)&xPlaneAddress, sizeof(xPlaneAddress));
+	if (numBytesSend >= 0) {
+		return numBytesSend;
+	} else {
+		fprintf(stderr, "Failed to send message (%d): %s", errno, strerror(errno));
+		return -1;
+	}
+}
+
+int recvFromXPlane(int sock, char msg[DGRAM_MSG_LENGTH], void *payload, int maxLength) {
+	char buf[maxLength + DGRAM_MSG_LENGTH];
+	memset(buf, 0, sizeof(buf));
+	int recvBytes = recv(sock, buf, maxLength + DGRAM_MSG_LENGTH, 0);
+	if (recvBytes >= 0) {
+		if (recvBytes >= DGRAM_MSG_LENGTH) {
+			memcpy(msg, &buf[0], DGRAM_MSG_LENGTH);
+			memcpy(payload, &buf[DGRAM_MSG_LENGTH], maxLength);
+			return recvBytes - DGRAM_MSG_LENGTH;
+		} else {
+			fprintf(stderr, "Received data without message header?!");
+			return -11;
+		}
+	} else {
+		fprintf(stderr, "Error receiving data (%d): %s", errno, strerror(errno));
+		return -1;
+	}
+
+}
+
+int createSocket(int srcPort) {
+	int xPlaneSocket;
+	struct sockaddr_in6 localAddress;
+
+	int err;
+
+	// create socket
+	xPlaneSocket = socket(AF_INET6, SOCK_DGRAM, 0);
+	if (xPlaneSocket == -1) {
+		fprintf(stderr, "Error creating socket (%d): %s\n", errno, strerror(errno));
+		return -1;
+	}
+
+	// prepare source address struct
+	localAddress.sin6_family = AF_INET6;
+	localAddress.sin6_port = htons(srcPort);
+	localAddress.sin6_addr = in6addr_any;
+
+	// bind to local port
+	err = bind(xPlaneSocket, (struct sockaddr *)&localAddress, sizeof(localAddress));
+	if (err) {
+		fprintf(stderr, "Error binding [::]:%d (%d): %s\n", srcPort, errno, gai_strerror(errno));
+		return -1;
+	}
+
+	return xPlaneSocket;
+}
+
+void closeSocket(int sock) {
+	close(sock);
+}

network.h

@@ -0,0 +1,17 @@
+#define DEST_SERVER "::1"
+#define DEST_PORT 49000
+#define SRC_PORT 49666
+
+#define SEND_BUFFER 512
+#define RECV_BUFFER 256
+
+#define DGRAM_MSG_LENGTH 4
+#define DGRAM_NULL_LENGTH 1
+
+extern const int DGRAM_MSG_START;
+extern const int DGRAM_PAYLOAD_START;
+
+int sendToXPlane(int sock, char *destAddr, int destPort, char *msg, void *payload, int lengthOfPayload);
+int recvFromXPlane(int sock, char msg[4], void *payload, int maxLength);
+int createSocket(int srcPort);
+void closeSocket(int sock);