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COMP445COMP445Fall 2006Fall 2006
Lab assignment 1
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STEP1: Get the name of the second party
STEP2: Get phone number from white pages
CALLER RECEIVER
STEP1: Plug the phone, and listen for incoming calls on a certain line
STEP3: Copy the number for your records
STEP4: Call the other party
ConnectionEstablished.
Chat…
STEP2: Get a call and accept it. “Caller ID” will give you the caller’s phone number.
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Program architectureProgram architecture
ClientServerport 7070
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Socket Programming
• Berkeley added a new interface to the operating system to support network communication. This interface is generally known as the Berkeley Sockets Interface and is the basis for almost all existing TCP/IP network protocol interfaces, including Windows Sockets
(commonly referred to as WinSock). • A socket is very much like a telephone - it's the endpoint
of a two-way communications channel. By connecting two sockets together you can pass data between
processes running on different computers.
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Main steps – client sideMain steps – client sideCreating a socket
SOCKET socket(int domain, int type, int protocol);
s = socket(AF_INET,SOCK_STREAM,0)
The structure we fill in is defined below.
struct sockaddr_in { short sin_family; // address family u_short
sin_port;// service port struct in_addr 16 bit TCP or UDP port number, network byte order
sin_addr; // internet address char 32 bits IPv4 address, Network Bytes Order
sin_zero[8]; // filler
}sa_in
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Main steps – client sideMain steps – client sideClient needs the address of the server.User inputs the server’s hostname.rp=gethostbyname(remotehost)
Fill in the server address memset(&sa_in,0,sizeof(sa_in)); memcpy(&sa_in.sin_addr,rp->h_addr,rp->h_length); sa_in.sin_family = rp->h_addrtype; sa_in.sin_port = htons(port); //port = 7070 host to network 16 bits
Connectingif (connect(s,(LPSOCKADDR)&sa_in,sizeof(sa_in)) == SOCKET_ERROR)
throw "connect failed\n"; Sending frames
ibytessent = send(s, (char*)&message_frame, sizeof(message_frame), 0);
Receiving frames
ibytesrecv = recv(s, (char*)& data_frame, sizeof(data_frame),0)
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Main steps – server sideMain steps – server side
Creating a socket
s = socket(AF_INET,SOCK_STREAM,0)
Fill in the server port and address info
sa.sin_family = AF_INET;
sa.sin_port = htons(port);
sa.sin_addr.s_addr = htonl(INADDR_ANY);
Bind the server port if (bind(s,(LPSOCKADDR)&sa,sizeof(sa)) == SOCKET_ERROR)
Listen for client requests if(listen(s,10) == SOCKET_ERROR)
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Main steps – server sideMain steps – server sideWatching for new messages
FD_SET(s,&readfds); //always check the listener if(!(outfds=select(infds,&readfds,NULL,NULL,tp))) {} else if (outfds == SOCKET_ERROR)
throw "failure in Select";
else if (FD_ISSET(s,&readfds))
cout << "got a connection request" << endl;
Accept the request
if((s1=accept(s,&ca.generic,&calen))==INVALID_SOCKET) throw "Couldn't accept connection\n";
Read a message
if((ibytesrecv = recv(s1,szbuffer,128,0)) == SOCKET_ERROR)
Send a message
if((ibytessent = send(s1,szbuffer,ibufferlen,0))== SOCKET_ERROR)
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Socket Functions
• int socket(int family, int type, int protocol);
returns: nonnegative descriptor if OK, -1 on error
• int connect(int sockfd, const struct sockaddr * servaddr, int addrlen);
return:0 if OK -1 on error
• int bind(int sockfd, const struct sockaddr * myaddr, int addrlen);
return: 0 if OK, -1 on error
• int listen(int sockfd, int backlog);
return: 0 of OK, -1 on error
• int accept(int sockfd, struct sockaddr * cliaddr, int * addrlen);
returns: nonnegative descriptor if OK,-1 on error
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CLIENT SERVERPURPOSE: File Transfer-Get a file-Send a file
•Should inform the server if the required action is to get a file from the server to upload a file to the server.•Should specify the name of theFile.•Respond to possible error messages.
•If a file is asked for, then it shouldsend an error message if file doesn’t exist.•If file exists, send it.•If file is being sent to you, save it.
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Transferring the data in and Transferring the data in and from the packet structurefrom the packet structure
Struct CONTROL_FRAME {unsigned char direction; //GET or PUTchar fname[MAX]; //filename
}
struct MESSAGE_FRAME {unsigned char header; //ERROR,DATA,LASTPACKET, etc.char data[MAX_SIZE]; //data or error message
} message_frame;
YOU ARE FREE TO DESIGN YOUR OWN STRUCTURES
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Reading from a fileReading from a filevoid main( void ) {
FILE *stream;
int numread, numwritten;
if( (stream = fopen( "fread.out", "r+b" )) != NULL ) {
…
numread = fread(message_frame.data,sizeof(char), MAX_SIZE, stream);
…}
else
printf( "File could not be opened\n" );
…}
fclose( stream );
}
Be careful if you use strcpy when reading from a binary file use memcpy.
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Writing in a fileWriting in a filevoid main( void ) {
FILE *stream;
int numread, numwritten;
if( (stream = fopen( "fread.out", "w" )) != NULL ) {
…
numwritten = fwrite(szbuffer, sizeof(char), MAX_SIZE, stream );
…}
else{
printf( "Problem opening the file\n" );
…}
fclose( stream );
}
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Decrypting the headerDecrypting the headerUse a switch to treat each of the cases:
switch (message_frame.header){
case 1 : …; break;
case 2 : …; break;
case 3 : …; break;
…………………………………………………………………………
default: …
}
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HintsHints• Use a log file in each side in order to
monitor all the actions:– receiving a packet– sending a packet, etc.
• Open and close the log file after each read/write operation if your program freezes and you cannot read the log file.
• Do not use any string library function! You will be able to send only text files but not binary ones (jpeg or exe for example).
• Instead use memcpy for transferring data.• Do not care about the order of the receiving
packets in this assignment (TCP will do it for you).
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Assignment 1
• No GUI
• Use Visual C++ 6
• Groups of NOT more than 2• wsock32.lib or you add the following
command to your code:#pragma comment(lib,"wsock32.lib")
• Implement only whatever you’re asked to do.
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Multi-thread in Windows
uintptr_t _beginthread( void( __cdecl *start_address )( void * ), unsigned stack_size, void *arglist );
Parameters:
start_address
Start address of routine that begins execution of new thread.
stack_size
Stack size for new thread or 0.
arglist
Argument list to be passed to new thread or NULL.
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The C++ Thread Class provided to you#define STKSIZE 16536class Thread{ public:Thread(){}
virtual ~Thread() {}static void * pthread_callback (void * ptrThis);virtual void run () =0 ;void start();
};
void * Thread::pthread_callback (void * ptrThis) { if ( ptrThis == NULL ) return NULL ; Thread * ptr_this =(Thread *)(ptrThis) ; ptr_this->run(); return NULL;} void Thread::start () { int result; if(( result = _beginthread((void (*)(void *))Thread::pthread_callback,STKSIZE,this ))<0)
{printf("_beginthread error\n");exit(-1);
} }
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How to make _beginthread work in VC6.00++
Right click the project and go to the Setting->C/C++->Category. Change the Category to “Code Generation” and change Use run-time library to “Multithreaded”.Note:You will encounter such a error “error C2065: '_beginthread' : undeclared identifier” at the compile time if you don’t do the above setting.
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