1 / 19

COMP445 Fall 2006

COMP445 Fall 2006. Lab assignment 1. CALLER. RECEIVER. STEP1: Get the name of the second party. STEP1: Plug the phone, and listen for incoming calls on a certain line. STEP2: Get phone number from white pages.

Download Presentation

COMP445 Fall 2006

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. COMP445Fall 2006 Lab assignment 1

  2. CALLER RECEIVER STEP1: Get the name of the second party STEP1: Plug the phone, and listen for incoming calls on a certain line STEP2: Get phone number from white pages STEP2: Get a call and accept it. “Caller ID” will give you the caller’s phone number. STEP3: Copy the number for your records Connection Established. Chat… STEP4: Call the other party

  3. Program architecture Server port 7070 Client

  4. 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.

  5. Main steps – client side Creating 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 ordersin_addr; // internet address char 32 bits IPv4 address, Network Bytes Order sin_zero[8]; // filler }sa_in

  6. Main steps – client side Client 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 = 7070host to network 16 bits Connecting if (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)

  7. Main 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)

  8. Main steps – server side Watching 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)

  9. 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

  10. CLIENT SERVER • PURPOSE: 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 the • File. • Respond to possible error messages. • If a file is asked for, then it should • send an error message if file doesn’t exist. • If file exists, send it. • If file is being sent to you, save it.

  11. Transferring the data in and from the packet structure Struct CONTROL_FRAME { unsigned char direction; //GET or PUT char 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

  12. Reading from a file void 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.

  13. Writing in a file void 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 ); }

  14. Decrypting the header Use a switch to treat each of the cases: switch (message_frame.header){    case 1 : …;        break;    case 2 : …;        break;    case 3 : …;        break; ………………………………………………………………………… default: … }

  15. Hints • 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).

  16. 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.

  17. 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.

  18. The C++ Thread Class provided to you #define STKSIZE 16536 class 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); } }

  19. 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.

More Related