UNIX Socket

(Cont.) (client-server) (client) (server)

(Cont.)Client server client server server clientClient server server clientServer client client serverserver Server (Ex: file server)

Cloud

{ 1

h

h

h

Internet

A{ 1

h

h

h

{ 2

h

h

h

A{ 2

(identifier) client client server server client

(Cont.)TCP 16 bits (protocol port number) server TCP

concurrency () (thread) concurrency client client client client thread thread thread

thread thread concurrent

(Cont.) N client N+1 thread

TCP client port number TCP segment client port number TCP segment (source port) port number (destination port) TCP client client

connection oriented connectionless client connection oriented connectionless

()

(Cont.)

(API)API (Application Program Interface) API (procedure) API API API API

Socket APISocket API BSD UNIX Berkley Univ. UNIX TCP/IP (procedure) OS Microsoft Windows (Winsock) UNIX OS (Ex: Solaris) socket API sockets

Sockets Socket Socket BSD Unix OS socket Unix OS socket OS socket API socket OS socket Socket socket API socket ()

Sockets Socket (Cont.) socket OS OS socket socket

Socket UNIX I/OUNIX socket I/O UNIX I/O open-read-write-close open descriptor read write

Socket UNIX I/O (Cont.) socket descriptor socket socket client server socket (option) socket

socket

A{

getprotobyname

socket

bind

listen

accept

send

close

{

gethostbyname

getprotobyname

socket

connect

recv

close

Socket API Functions gethostname int gethostname(char *name, int namelen)struct protoent *getprotobyname(const char *name) returns a pointer to a protoent structure (protocol entity)the members of which contain the fields of an entry in the network protocol database. accept getpeername client

Socket API Functions (Cont.)Socket socket descriptordescriptor = socket (protofamilytypeprotocol)Protofamily socket PF_INET (AF_INET) TCP/IP protocolPF_DECnet DEC type socket connection-oriented data stream ( SOCK_STREAM) connectionless message ( SOCK_DGRAM)

Socket API Functions (Cont.)Protocol socket Specifying a protocol of 0 causes socket() to use an unspecified default protocol appropriate for the requested socket type (e.g., TCP/IP).

Socket API Functions (Cont.)close socket (Winsock closesocket)close (socket)socket socket descriptor socket connection-oriented close socket socket

Socket API Functions (Cont.)bind socket bind socket port server port bind (socketlocaladdraddrlen)socket port number descriptorlocaladdr addrlen

Socket API Functions (Cont.) socket socket API sockaddr struct sockaddr { /* IPv4 */ u_char sa_len; /* total length of the address */ u_char sa_family; /* family of the address */ char sa_data[14]; /* the address itself */ };

Socket API Functions (Cont.)struct socketaddr_in { u_char sa_len; u_char sa_family; u_short sin_port; struct inaddr sin_addr; /* IP address of the computer */ char sin_zero[8]; /*unused, for padding with the same size as sockaddr */ };

Socket API Functions (Cont.)multihomed capabilityIP IP MAC Multi-homed IP Support . IP/Hostname, ftp.heaven.netftp.hell.netMulti-homed IP Support Login IP Anonymous Login Hostname

Socket API Functions (Cont.) (multi-homed) IP socket API INADDR_ANY IP IP port number

Socket API Functions (Cont.)listen port number (ex: bind) OS socket client listen (socketqueuesize)socket port number descriptorqueuesize socket (request queue) OS request queue request queue request queue

Socket API Functions (Cont.)accept connectionless socket bind connection-oriented listen socket client

Socket API Functions (Cont.) connection-oriented accept client request queue accept client client server newsock=accept (socketcaddresscaddresslen)socket descriptorcaddress sockaddr caddresslen

Socket API Functions (Cont.)accept caddress caddresslen socket socket descriptor socket descriptor socket socket socket socket

Socket API Functions (Cont.)connect connect connect (socketsaddresssaddresslen)socket socket descriptorsaddress sockaddr saddresslen sockaddr connection-oriented TCP connect connect accept

Socket API Functions (Cont.) connectionless connect socket socket connectionless connect connectionless client

Socket API Functions (Cont.)send socket send send (socket*datalengthflags)data length flags flags 0 0MSG-OOB (out of band)MSG_PEEKMSG_PEEKrecvrecvfrom MSG_DONTROUTE local routing table

Socket API Functions (Cont.)sendto sendmsg client server connectionless sendto (socket*datalengthflags*destaddressaddresslen)sendmsg sendto sendmsg (socket*msgstructflags)

Socket API Functions (Cont.)msgstruct msghdr struct msghdr { void *msg_name; /* protocol address */ socklen_t msg_namelen; /* size of protocol address */ struct iovec *msgiov; /* scatter/gather array */ size_t msg_iovlen; /* # elements in msg_iov */ void *msg_control; /* ancillary data */ socketlen_t msg_controllen; /* length of ancillary data */ int msg_flags; /* flags returned by recvmsg() */};

Socket API Functions (Cont.)msg_name points to a data structure which the sender stores the destination addressmsgiov msg_iovlen array of input/output buffer (buffer iovec structure)struct iovec { void *iov_base; /* starting address of buffer */ size_t iov_len;}msg_control msg_controllen (E.g., hop limit, next hop address)msg_flags recvmsg sendmsg

Socket API Functions (Cont.)recv recv socket recv (socket*bufferlengthflags)buffer length buffer flags MSG_OOBMSG_PEEKrecvfrom socket client recvfrom

Socket API Functions (Cont.)recvfrom (socket*bufferlengthflags*sndaddress*saddrlen) sndaddress saddrlen recvfrom sendto recvfrom

Socket API Functions (Cont.)sendmsg recvmsg recvfrom recvmsg (socket*msgstructflags)msgstruct sendmsg

Socket Socket read/write /read write socket descriptorread write socket read/write descriptor descriptor socket I/O

socket socket optionssetsockopt socket option setsockopt socket option setsockopt(socketleveloptnameoptvaloptlen)level= SOL_SOCK or TCP leveloptionsSO_BROADCAST (broadcast)SO_KEEPALIVE (keeps connections active by enabling the periodic transmission of messages)

socket (Cont.)gethostbyaddr gethostbyname IP

Socketthread thread thread socketSocket reference count socket socket reference count 1 reference countsocket process/thread parent child process reference count 1

Socketthread (Cont.)Status of client-server before call to accept returnsclientconnect()serverlistenfdconnectionrequest

Socketthread (Cont.)Status of client-server after return from acceptclientconnect()serverlistenfdconnectionconnfd

Socketthread (Cont.)Status of client-server after fork returns

clientconnect()serverlistenfdconnectionconnfdlistenfdconnfdforkserver(child)

Socketthread (Cont.)Status of client-server after parent and child close appropriate socketsclientconnect()serverlistenfdconnectionconnfdserver (child)

Socketthread (Cont.) process/thread socket close reference count thread thread socket thread socket close

Socket Functions for Elementary TCP Client-Server

socket()

TCP client

connect()

write()

read()

close()

socket()

TCP server

listen()

accept()

read()

write()

bind()

read()

well-known port

blocks until connection from client

connection establishmentTCP three-way handshake

data (request)

process request

data (reply)

end-of-file notification

close()

Socket Functions for UDP Client-Server

socket()

UDP client

sendto()

recvfrom()

close()

socket()

UDP server

recvfrom()

sendto()

bind()

well-known port

blocks until datagram received from a client

data (request)

process request

data (reply)

An ExampleA Simple Daytime Client#include unp.h int main (int argc, char **argv) { int sockfd, n; char recvline[MAXLINE+1]; struct sockaddr_in servaddr; if(argc!=2) err_quit(usage: a.out );

An ExampleA Simple Daytime Client (Cont.) if((sockfd=socket(AF_INET, SOCK_STREAM,0)) < 0) err_sys(socket error);

bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family=AF_INET; servaddr.sin_port=htons(13); if(inet_pton(AF_INET, argv[1], &servaddr.sin_addr)

An ExampleA Simple Daytime Client (Cont.) while ((n=read(sockfd, recvline, MAXLINE)) >0) { recvline[n]=0; /* null terminate */ if (fputs(recvline, stdout) = = EOF) err_sys(fputs error); } if (n>0) error_sys(read error); exit(0); }

An ExampleA Simple Daytime Server#include unp.h #include

int main(int argc, char **argv) { int listenid, connfd; struct sockaddr_in servaddr; char buf[MAXLINE]; time_t ticks;

listenid=socket(AF_INET, SOCK_STREAM,0);

An ExampleA Simple Daytime Server (Cont.) bzero(&servaddr, sizeof(servaddr)); servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(13);

bind(listenid, (SA *)&servaddr, sizeof(servaddr));

listen(listenfd, LISTENQ); for( ; ; ) { connfd=accept(listenfd, (SA *)NULL, NULL);

An ExampleA Simple Daytime Server (Cont.) ticks=time(NULL); snprintf(buff, sizeof(buff), %.24s\r\n, ctime(&ticks)); write(connfd, buff, strlen(buff));

close(connfd); } }

ReferenceUNIX Network Programming:Networking APIsSockets and XTI, W. R. StevensPH. PTR1998.