Design, implementation and evaluation issues of local area network devices 期末 DEMO

1. Design, implementation and evaluation issues of local area network devices 期末DEMO Elementary SCTP Socket Functions & Client/Server Example 694430007 陳旻槿

2. SCTP Socket Types • Maintain consistency with the existing sockets APIs • The SCTP sockets API extension must stay consistency with the existing UDP,TCP,IPv4,and IPv6 sockets API. • SCTP socket API comes in two forms: one-to-one and one-to-many. • The one-to-one used to be called the a “TCP style” socket. • The one-to-many at one time was known by the “UDP style” socket.

3. Functions Discussion socket() • Applications calls socket() to create a socket descriptor to represent an SCTP endpoint. bind() • Applications use bind() to pass an address to be associated with an SCTP endpoint to the system. listen() • Applications use listen() to ready the SCTP endpoint for accepting inbound associations. accept() • Applications use accept() call to remove an established SCTP association from the accept queue of the endpoint.

4. Functions Discussion connect() • Applications use connect() to initiate an association to a peer. sendmsg() and recvmsg() • An application uses sendmsg() and recvmsg() call to transmit data to and receive data from its peer. close() • Applications use close() to gracefully close down an association. sctp_bindx() • Allows an application to bind a set of addresses instead of one or all addresses.

5. sctp_initmsg() • SCTP_INITMSG – Can be used to get or set the default INIT/INIT-ACK settings such as number of streams allowed in or requested out. sctp_sendmsg() • This call will allow the caller to specify on the command line things like the stream number and other SCTPish information to be sent with a message. sctp_recvmsg() • This call is used to receive a message but also a sctp_sndrcvinfo structure with details on the message (e.g. The stream number and stream sequence number).

6. SCTP one-to-one style socket • A typical server in one-to-one style uses the following system call sequence to prepare an SCTP endpoint for servicing requests: 1. socket() 2. bind() 3. listen() 4. accept() 5. close()

7. A typical client uses the following system call sequence to setup an association with a server to request services: 1. socket() 2. connect() 3. close() • After returning from connect(), the client uses send and recv calls to send out requests and receive responses from the server.

8. Server(connection-oriented protocol) socket() single addresses multiple addresses Client (connection-oriented protocol) bind() sctp_bindx() listen() socket() accept() blocks until connection from client SCTP_INITMSG connect() data (request) send() or sendmsg() recv() or recvmsg() process request data (reply) send() or sendmsg() recv() or recvmsg() close() close()

9. one-to-many style socket • A typical server using a one-to-many style socket will do a socket() call, followed by a listen() and sendmsg() / recvmsg(). • Note that the connect() and accept() call are not needed. • A typical server in this style uses the following socket calls in sequence to prepare an endpoint for servicing requests: 1. socket() 2. bind() 3. listen() 4. recvmsg() and sendmsg() 5. close()

10. A typical client uses the following calls in sequence to setup an association with a server to request services: • 1. socket() • 2. sendmsg() • 3. recvmsg() • 4. close()

11. Server socket() bind() Client listen() socket() data (request) sendto( )/ sendmsg() recvfrom() / recvmsg() process request data (reply) sendto( )/ sendmsg() recvfrom() / recvmsg() close() close()

12. Multi-streaming demo • This example presents a server that implements a form of the daytime protocol. • This traditional server emits the current time to a connected client, but for SCTP, I emit the local time on stream 0 and Greenwich Mean Time (GMT) on stream 1.

13. Server Client socket() socket() bind() listen() Connection establishment accept() connect() Stream 0 sctp_ sendmsg() Sctp_recvmsg Stream 1 sctp_ sendmsg() Sctp_recvmsg Connection termination close() close() Sockets functions used in the multi-streaming daytime server and client

14. Server code (1/2) • int main() • { • int listenSock, connSock, ret; • struct sockaddr_in servaddr; • char buffer[MAX_BUFFER+1]; • time_t currentTime; • /* Create SCTP TCP-Style Socket */ • listenSock = socket( AF_INET, SOCK_STREAM, IPPROTO_SCTP ); • /* Accept connections from any interface */ • bzero( (void *)&servaddr, sizeof(servaddr) ); • servaddr.sin_family = AF_INET; • servaddr.sin_addr.s_addr = htonl( INADDR_ANY ); • servaddr.sin_port = htons(MY_PORT_NUM); • /* Bind to the wildcard address (all) and MY_PORT_NUM */ • ret = bind( listenSock,(struct sockaddr *)&servaddr, sizeof(servaddr) ); • /* Place the server socket into the listening state */ • listen( listenSock, 5 );

15. Server code (2/2) • /* Server loop... */ • while( 1 ) { • /* Await a new client connection */ • connSock = accept( listenSock,(struct sockaddr *)NULL, (int *)NULL ); • /* New client socket has connected */ • /* Grab the current time */ • currentTime = time(NULL); • /* Send local time on stream 0 (local time stream) */ • snprintf( buffer, MAX_BUFFER, "%s\n", ctime(&currentTime) ); • ret = sctp_sendmsg( connSock,(void *)buffer, (size_t)strlen(buffer), • NULL, 0, 0, 0, LOCALTIME_STREAM, 0, 0 ); • /* Send GMT on stream 1 (GMT stream) */ • snprintf( buffer, MAX_BUFFER, "%s\n", asctime( gmtime( &currentTime ) ) ); • ret = sctp_sendmsg( connSock,(void *)buffer, (size_t)strlen(buffer), • NULL, 0, 0, 0, GMT_STREAM, 0, 0 ); • /* Close the client connection */ • close( connSock ); • } • return 0;}

16. Client code (1/2) • int main() • { • int connSock, in, i, flags; • struct sockaddr_in servaddr; • struct sctp_sndrcvinfo sndrcvinfo; • struct sctp_event_subscribe events; • char buffer[MAX_BUFFER+1]; • /* Create an SCTP TCP-Style Socket */ • connSock = socket( AF_INET, SOCK_STREAM, IPPROTO_SCTP ); • /* Specify the peer endpoint to which we'll connect */ • bzero( (void *)&servaddr, sizeof(servaddr) ); • servaddr.sin_family = AF_INET; • servaddr.sin_port = htons(MY_PORT_NUM); • servaddr.sin_addr.s_addr = inet_addr( "127.0.0.1" ); • /* Connect to the server */ • connect( connSock, (struct sockaddr *)&servaddr, sizeof(servaddr) ); • /* Enable receipt of SCTP Snd/Rcv Data via sctp_recvmsg */ • memset( (void *)&events, 0, sizeof(events) ); • events.sctp_data_io_event = 1; • setsockopt( connSock, SOL_SCTP, SCTP_EVENTS, • (const void *)&events, sizeof(events) );

17. Client code (1/2) • /* Expect two messages from the peer */ • for (i = 0 ; i < 2 ; i++) { • in = sctp_recvmsg( connSock, (void *)buffer, sizeof(buffer), • (struct sockaddr *)NULL, 0, • &sndrcvinfo, &flags ); • /* Null terminate the incoming string */ • buffer[in] = 0; • if (sndrcvinfo.sinfo_stream == LOCALTIME_STREAM) { • printf("(Local) %s\n", buffer); • } else if (sndrcvinfo.sinfo_stream == GMT_STREAM) { • printf("(GMT ) %s\n", buffer); } • } • /* Close our socket and exit */ • close(connSock); • return 0; • }