Sending data - TCP connection
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Hey all, I have implemented a simple TCP server/client class from the following web-site (http://www.codeproject.com/internet/winsockintro02.asp). Which shows us how to send raw
char*data over the TCP connection. My problem is that I want to be able to send a whole instance of a class, for exampleClassFoo objectFoo;i.e. I want to be able to send the object:objectFoo, instead of just text, i.e. "hello". Can anyone help me, by hinting how to achieve this ? Thanks -
You need to do what is frequently referred to as "Marshalling", in other words, you need to convert an instance of your class into a byte stream, and then, when you recv this byte stream from a source, you need to be able to "reconstitute" it. Look up marshalling for ideas on how to do this. COM supports this and performs it automatically (as well as allowing you to customize the process if you're crazy enough). I think .Net supports this as well. There are C++ frameworks that also support this, you can look for them.
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Jim Crafton wrote:
You need to do what is frequently referred to as "Marshalling"
:confused: Isn't marshalling used in terms of memory where reconstituting objects is referred to as serialization?
Actually I was going to ask you the same question! I was going to say "serialization" but then I *thought* (always a dangerous idea) that serialization was just a way to store object data, not necessarily create a new object from scratch. Whereas marshalling was actually the ability to send the object across the wire with all the info needed to completely recreate it from scratch on the other side. Now that I think about it, I suspect I'm getting my "definition" from how COM does things, which may or may not be the way most other OO frameworks/libraries do things.
¡El diablo está en mis pantalones! ¡Mire, mire! Real Mentats use only 100% pure, unfooled around with Sapho Juice(tm)! SELECT * FROM User WHERE Clue > 0 0 rows returned Save an Orange - Use the VCF! VCF Blog
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bigdenny200 wrote:
Can anyone help me, by hinting how to achieve this ?
It's called "Serialization". You might want to use it as a keyword in Google and read some material to gain a basic understanding of it.
Dear led, thanks for reply. I found a tutorial, which should have done a serialization, as you suggested. Below is the code (with my object, instead the one from tutorial):
// Serialize the object std::vector word\_list; word\_list.push\_back(\_T("HI")); ofstream ofs("c:\\\\fifthgrade.ros", ios::binary); ofs.write((char \*)&word\_list, sizeof(word\_list)); // Deserialize it std::vector word\_list2; ifstream ifs("c:\\\\fifthgrade.ros", ios::binary); ifs.read((char \*)&word\_list2, sizeof(word\_list)); // last lineThe problem is that this code (the last line) doesnt work. And I think this is because I am using not simple Class instances, but a
vectorobject. Do you have any idea, what could be other reason for it not to work ? thanks -
Dear led, thanks for reply. I found a tutorial, which should have done a serialization, as you suggested. Below is the code (with my object, instead the one from tutorial):
// Serialize the object std::vector word\_list; word\_list.push\_back(\_T("HI")); ofstream ofs("c:\\\\fifthgrade.ros", ios::binary); ofs.write((char \*)&word\_list, sizeof(word\_list)); // Deserialize it std::vector word\_list2; ifstream ifs("c:\\\\fifthgrade.ros", ios::binary); ifs.read((char \*)&word\_list2, sizeof(word\_list)); // last lineThe problem is that this code (the last line) doesnt work. And I think this is because I am using not simple Class instances, but a
vectorobject. Do you have any idea, what could be other reason for it not to work ? thanksbigdenny200 wrote:
I found a tutorial
Please provide a link. Either it is not adequate or you have not understood it correctly. I would think most people would take longer than a single hour of studying to understand serialization. You are trying to understand it right? Not just trying to reproduce the tutorial source code for your purposes, that's not going to go well. You need to study it with the goal of understanding it.
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Actually I was going to ask you the same question! I was going to say "serialization" but then I *thought* (always a dangerous idea) that serialization was just a way to store object data, not necessarily create a new object from scratch. Whereas marshalling was actually the ability to send the object across the wire with all the info needed to completely recreate it from scratch on the other side. Now that I think about it, I suspect I'm getting my "definition" from how COM does things, which may or may not be the way most other OO frameworks/libraries do things.
¡El diablo está en mis pantalones! ¡Mire, mire! Real Mentats use only 100% pure, unfooled around with Sapho Juice(tm)! SELECT * FROM User WHERE Clue > 0 0 rows returned Save an Orange - Use the VCF! VCF Blog
Jim Crafton wrote:
Now that I think about it, I suspect I'm getting my "definition" from how COM does things, which may or may not be the way most other OO frameworks/libraries do things.
Well I just checked an according to the Wikipedia they are interchangeable. From my experience I learned about marshalling way back in Remote Procedure Calls and Serialization came later in terms of Objects so I made the connection that way. Learn something new everyday.
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bigdenny200 wrote:
I found a tutorial
Please provide a link. Either it is not adequate or you have not understood it correctly. I would think most people would take longer than a single hour of studying to understand serialization. You are trying to understand it right? Not just trying to reproduce the tutorial source code for your purposes, that's not going to go well. You need to study it with the goal of understanding it.
I agree with what you are saying, but the problem is that I am working on a project which is due soon. And I cant devote too much time to serialization only. But, in this case, I really thought that using the tutorial was supposed to work and would suffice. Here it is: http://www.functionx.com/cpp/articles/serialization.htm, and it seemed pretty easy for me from here. Thanks
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I agree with what you are saying, but the problem is that I am working on a project which is due soon. And I cant devote too much time to serialization only. But, in this case, I really thought that using the tutorial was supposed to work and would suffice. Here it is: http://www.functionx.com/cpp/articles/serialization.htm, and it seemed pretty easy for me from here. Thanks
Yeah, I would not recommend that tutorial. The example "class" used is not a class, it is a simple 'C' data structure and there has been intrinsic support for reading and writing 'C' data structures since.... well 'C'. That is not the same thing as 'Serialization' of complex C++ classes that may contain pointers which are memory addresses. You cannot serialize a memory address. You must serialize/deserialize the data at the memory address which requires knowledge of the data structure. Knowledge of the data structure is something that only the developer has meaning you cannot rely on the compiler to properly serialize your class.
bigdenny200 wrote:
but the problem is that I am working on a project which is due soon. And I cant devote too much time to serialization only.
I can't help the fact that poor project management and planning conflicts with reality. I am only a software developer not a magician that can bend time and warp reality. Perhaps your situation now calls for the Post Agile Manifesto approach to software development[^]. I don't recommend it, but if that's what you must do.... whatever.
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Yeah, I would not recommend that tutorial. The example "class" used is not a class, it is a simple 'C' data structure and there has been intrinsic support for reading and writing 'C' data structures since.... well 'C'. That is not the same thing as 'Serialization' of complex C++ classes that may contain pointers which are memory addresses. You cannot serialize a memory address. You must serialize/deserialize the data at the memory address which requires knowledge of the data structure. Knowledge of the data structure is something that only the developer has meaning you cannot rely on the compiler to properly serialize your class.
bigdenny200 wrote:
but the problem is that I am working on a project which is due soon. And I cant devote too much time to serialization only.
I can't help the fact that poor project management and planning conflicts with reality. I am only a software developer not a magician that can bend time and warp reality. Perhaps your situation now calls for the Post Agile Manifesto approach to software development[^]. I don't recommend it, but if that's what you must do.... whatever.
> I can't help the fact that poor project management and planning conflicts with reality. I am >only a software developer not a magician that can bend time and warp reality. Perhaps your >situation now calls for the Post Agile Manifesto approach to software development[^]. I don't >recommend it, but if that's what you must do.... whatever. There is no project management, its a University project. Had a lazy life before ;) So now, I am tight in my deadlines.
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> I can't help the fact that poor project management and planning conflicts with reality. I am >only a software developer not a magician that can bend time and warp reality. Perhaps your >situation now calls for the Post Agile Manifesto approach to software development[^]. I don't >recommend it, but if that's what you must do.... whatever. There is no project management, its a University project. Had a lazy life before ;) So now, I am tight in my deadlines.
bigdenny200 wrote:
So now, I am tight in my deadlines.
Hmm....in the 5 hours this thread has been around, you probably could have researched and implemented serialization for a class ;P Whether or not you use MFC, I would take a look at Serialization (MFC)[^] This is an example of a fairly robust, generic, serialization solution. On the other (easy) end of the solution spectrum, you could simply add a serialize method and an unserialize method to your class, both of which take a socket as a parameter. The serialize method would write (binary) all the class' data, one at a time, to the socket. The unserialize method would read the binary data into the class' members, in the same order it was serialized. That's a simple, socket-only class serialization solution. led mike...sorry for posting in your thread :) Mark
Mark Salsbery Microsoft MVP - Visual C++ :java:
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bigdenny200 wrote:
So now, I am tight in my deadlines.
Hmm....in the 5 hours this thread has been around, you probably could have researched and implemented serialization for a class ;P Whether or not you use MFC, I would take a look at Serialization (MFC)[^] This is an example of a fairly robust, generic, serialization solution. On the other (easy) end of the solution spectrum, you could simply add a serialize method and an unserialize method to your class, both of which take a socket as a parameter. The serialize method would write (binary) all the class' data, one at a time, to the socket. The unserialize method would read the binary data into the class' members, in the same order it was serialized. That's a simple, socket-only class serialization solution. led mike...sorry for posting in your thread :) Mark
Mark Salsbery Microsoft MVP - Visual C++ :java:
Mark Salsbery wrote:
On the other (easy) end of the solution spectrum, you could simply add a serialize method and an unserialize method to your class, both of which take a socket as a parameter.
But that will ofcourse only work if the class contains no pointers or virtual functions. If you have already a successful way to save and retrieve to and from a file, your're nearly there if you have no virtual functions. Just use the same code to write to and retrieve from the socket. Hope you get it together in time :)
Bram van Kampen