Transferring a file through TCP in GCDAsyncSocket - ios

Question

I am currently writing a game in which I intend to transfer a .caf sound file from the iPhone to my C++ server. Right now I am getting an EXC_BAD_ACCESS when I message the sendGameUpdateWithFile function, and I really have no idea why.
Although this is not related to any uni assignments, please keep in mind that I am a CS student and not (yet) a professional network programmer, so judge my code thereafter.
Here's the code I use to transmit the data to the server (which crashes right now):
- (void) sendGameUpdateWithFile:(NSString*)filePath gameID:(NSInteger)gameID {
NSMutableData* data = [[NSMutableData alloc] init];
data = [NSMutableData dataWithContentsOfFile:filePath];
fileheadPacket head;
head.msgtype = 0x12;
strncpy(head.data1, [myUsername cStringUsingEncoding:NSASCIIStringEncoding], [myUsername length]);
int followingPackets = (([data length] % 1024 == 0) || ([data length] < 1024))? ([data length]/1024) : ([data length]/1024)+1;
head.following = followingPackets;
head.fileid = gameID;
head.size = sizeof(packet);
[mySock writeData:[NSData dataWithBytes:&head length:sizeof(packet)] withTimeout:-1 tag:7];
filePacket sendPackets[followingPackets];
for(int i = 0; i < followingPackets; i++){
NSRange thisRange;
thisRange.location = i*1024;
thisRange.length = (i+1)*1024;
filePacket tmp;
tmp.msgtype = 0x13;
tmp.size = sizeof(filePacket);
memset(tmp.data1, 0, sizeof(tmp.data1));
[data getBytes:tmp.fileBuffer range:thisRange];
strncpy((char*)&sendPackets[i], (char*)&tmp, sizeof(tmp));
}
for(int i = 0; i < followingPackets; i++){
[mySock writeData:[NSData dataWithBytes:&sendPackets[i] length:sizeof(filePacket)] withTimeout:-1 tag:3];
}
}
The structs I use for data look like this:
typedef struct file_packet {
int msgtype:8;
int size:16;
int nul:8;
int following:24;
int emp:8;
char data1[64];
char fileBuffer[1024];
} filePacket;
typedef struct filehead_packet {
int msgtype:8;
int size:16;
int nul:8;
int following:24;
int emp:8;
char data1[64];
int fileid;
char rest[60];
} fileheadPacket;
The server expects the given msgtypes -- the problem lies on the client side.