I try to solve this but again some errors came out!!

Can anyone help me?



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What are the errors?
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Sorry that i didn't post the errors!!!


cc: Error: program3.c, line 41: Invalid declarator. (declarator)
packet.ver = 4;
------^
cc: Error: program3.c, line 42: Invalid declarator. (declarator)
packet.ihl = 5;
------^
cc: Error: program3.c, line 43: Invalid declarator. (declarator)
packet.tos = 0;
------^
cc: Error: program3.c, line 44: Invalid declarator. (declarator)
packet.length = htons(0x4321);
------^
cc: Error: program3.c, line 45: Invalid declarator. (declarator)
packet.identification = htons(0x9876);
------^
cc: Error: program3.c, line 46: Invalid declarator. (declarator)
packet.flag_offset = 0;
------^
cc: Error: program3.c, line 47: Invalid declarator. (declarator)
packet.ttl = 64;
------^
cc: Error: program3.c, line 48: Invalid declarator. (declarator)
packet.protocol = 6;
------^
cc: Error: program3.c, line 49: Invalid declarator. (declarator)
packet.checksum = htons(0x1111);
------^
cc: Error: program3.c, line 50: Invalid declarator. (declarator)
packet.source = htonl(0xc0a8fa03);
------^
cc: Error: program3.c, line 51: Invalid declarator. (declarator)
packet.destination = htonl(0xc0a8faa8);
------^
cc: Error: program3.c, line 60: In this statement, "packet" is declared as a typedef, and so cannot occur as an expression. (typeexpr)
ptr = (char*)&packet;
--------------^




The variable that you have declared is of type packet and the name is frame. Not the opposite.
Simply change the variable name where is indicated from packet.* to frame.*
Hope this help you

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Hi..Thanks for the reply but I'm afraid that didn't solve the errors....

Can you or someone else give me specific information about that?

Thankss

The problem with the code is stated above so I will assume that you need help understanding the problem.

First off lets talk about style:
There are a number of stylistic choices that programmers have made over the years that have become rather standard. The reason is that they have proven to be "best practices". By adopting some of these style habits we can correct and avoid many of the problems in your code.

Normally the typedef would not be done inside of the main() function. The reason is that if you define it inside of main() then it can only be used inside of main() and this limits your ability to create modular programs. But if the typedef is placed before the main() function (or in an include file) then it can be used throughout the file.

Additionally, we normally give typedef aliases names that begin with a capital (as apposed to variables which we always begin with a lower case letter). This makes the beginning of your program look like this:



Note that 'packet' has become 'Packet'. Also note that I have used indentation between brackets '{ }' so that the blocks of code stand out on their own. This will help us keep track of opening and closing of brackets, but it will also help our eyes catch blocks of code.

Now you seem to use two variables of type 'Packet' in your program, one is named 'frame', the other named 'packet'. So I defined a second variable.

The next thing I noted is that you have an independant block... This is a little odd (there were popular once for controlling scope but I never noted them much in C). You don't use the block for any particular purpose, so I got rid of it, in the process I discovered a problem with your IP Packet structure...

First of all you may wish to look at the definition of the structure. Note that the last two arrays are not part of the structure, they should be 32 bit integers.

Unfortunately C has these wonderful data types, but they don't DEFINE the size of the types. We more or less assume that 1 byte is 8 bits, and a short int is 16, a long int 32... but this is NOT always the case. If you look in ip.h you will see that they define the packet structure thus:Come to think of it, why arn't you using the ip packet defined in ip.h?

anyway here is what I came up with after fixing all the syntax errors I could find (note that I needed to use the windows lib rather than the unix one):

Thanks very much NickDMax for this all usefull information you posted!!

I look again to it but I have to modified the program this way!!



Can you look it again for me pls?

I compile it and it cames with one error only this time..!

cc: Error: program3.c, line 29: In this statement, "frame.ucDestination" has an unsigned long type, but occurs in a context that requires a pointer. (needpointer)
frame.ucDestination[iLoop] = (unsigned char)iLoop;
^

Thanks!

I think what you were trying to do was something like this:

note that Packet::ucDestination is not an array... but we want to cheat a little and put data into it byte-by-byte... so we are going to use a char pointer to point to its address. Note normally this is NOT the best way to do this. One thing that comes to mind is Big Endian vs Little Endian, because of how the computers will store data in memory (some computers put the low byte at a lower address then the high byte, and some computers the other way so the low byte has a higher address than the high byte).

So I would say that you need to keep that in mind.

Hi again!

When I compile it it prints only

Octet0=

and then Segmentation fault!

I don't know why!

You new topic was deleted. Please do not post duplicate topics... esp. when you revert back to the original post.

If you are getting a segmentation fault then you are misusing pointers. Think carefully about what the pointers are pointing to. If you are not good at thinking carefully about pointers try using a debugger and watching the variables involved.

I will try to find time to look at it again. Though I have to tell you, seeing you post the same old code over again really made me not want to help you. You don't seem to be learning anything. It is not my job to fix your code, I don't mind helping you learn, but I get payed pretty darn good as a programmer. -- the errors we fixed in this code were very similar to your last post about Ethernet frame structure. You made the same mistakes in your IP packet program... you are not learning.