Transcript ppt - Pacific University

TCP
section 6.5
(Read this section!)
27 Feb 2007
CS 360 – Spring 2007
Pacific University
TCP
• Transmission Control Protocol (RFC 793/and many more)
• Reliable, connection-based protocol
– byte stream
– max packet size: 64 KB (1460 bytes is often the practical limit)
Tanenbaum, Figure 6-28, page 534
CS 360 – Spring 2007
Pacific University
Socket Libraries (Unix/Linux)
This is all the same, just like UDP!
#include <sys/types.h> // data types
#include <sys/socket.h> // socket interface
#include <netinet/in.h> // Internet interface
• The socket is the common Unix interface to the network
– a socket represents an end point for network communication
– Berkeley Software Distribution socket API
• 4.2 BSD Unix
• most OSes now provide a BSD socket interface for networking
– Microsoft Windows almost provides it
• defacto standard
– a socket is represented by an int
CS 360 – Spring 2007
Pacific University
API Usage: Call Sequences
• TCP over IP (connection-based):
socket()
bind()
listen()
accept()
recv()/send()
close()
socket()
connect()
send()/recv()
close()
server
client
CS 360 – Spring 2007
Pacific University
Socket library functions
• TCP over IP
– domain (protocol family): PF_INET
– type: SOCK_STREAM
– protocol: IPPROTO_TCP
• see /etc/protocols for a list
– address family: AF_INET
int socket(int domain, int type, int protocol)
int bind(int sockfd, const struct sockaddr *my_addr,
socklen_t addrlen)
– actually use struct sockaddr_in for IP networking
CS 360 – Spring 2007
Pacific University
Socket library functions
int listen(int sockfd, int backlog)
– backlog defines the length of the queue of pending connections
– If a connection request arrives with the queue full the client may
receive an error with an indication of ECONNREFUSED
int accept(int sockfd, struct sockaddr *addr,
socklen_t *addrlen)
– addr is the address of the incoming connection
– really use a struct sockaddr_in*
ssize_t send(int sockfd, const void *buf, size_t
len, int flags);
– flags sets some options
ssize_t recv(int sockfd, void *buf, size_t len, int
flags);
– flags sets some options: MSG_WAITALL, etc.
CS 360 – Spring 2007
Pacific University
Socket library functions
int connect(int sockfd, const struct sockaddr
*serv_addr, socklen_t addrlen);
– again, use struct sockaddr_in for IP connections
– this struct is filled with address information specifying the destination of the data
int close(int sockfd)
– just like closing a file
int setsockopt(int sockfd, int level, int ptname,
const void *optval,socklen_t optlen)
- #include <netinet/tcp.h>
–
–
–
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manipulate the options associated with a socket
level: SOL_TCP for options to TCP
man socket for full list of options
TCP_NODELAY: send data immediately
CS 360 – Spring 2007
Pacific University
•
Code:
Client!
page 490 has a TCP example
– it uses read/write rather than recv/send. why?
struct sockaddr_in sAddr;
int addrLen = sizeof(struct sockaddr_in);
int sock;
int connectStatus;
char buf[1024];
int bufLen = 1024;
sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
memset(&sAddr, 0, addrLen);
sAddr.sin_family = AF_INET;
sAddr.sin_port = htons(PORT);
sAddr.sin_addr.s_addr = inet_addr(“64.59.233.238”);
connectStatus = connect(sock, &sAddr,addrLen);
if( send(sock, (void)*buf, bufLen, 0) == -1) { }
if( recv(sock, (void)*buf, bufLen, MSG_WAITALL) == -1) { }
close(sock);
CS 360 – Spring 2007
Pacific University
Code: Server!
struct sockaddr_in sAddr;
int addrLen = sizeof(struct sockaddr_in);
int listenSock, dataSock, status, one = 1;
char buf[1024];
int bufLen = 1024;
listenSock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
status = setsockopt(listenSocket, SOL_TCP, TCP_NODELAY, &one, sizeof(int));
memset(&sAddr, 0, addrLen);
sAddr.sin_family = AF_INET;
sAddr.sin_port = htons(PORT);
sAddr.sin_addr.s_addr = NULL;
status = bind(listenSock, &sAddr, addrLen);
status = listen(listenSocket, 10);
dataSock = accept(listenSocket, &sAddr, &addrLen);
status = recv(dataSock, (void)*buf, bufLen, MSG_WAITALL);
status = send(dataSock, (void)*buf, bufLen, 0);
close(dataSock);
CS 360 – Spring 2007
close(listenSock);
Pacific University
Your Project
• A stream of MathPackets
– calculation stream
• Server needs to be multithreaded
– one thread per connection
• Server stores intermediate value for each stream
– perform calculations as the packets arrive
• A client can set a named value
– 4 character name (exactly)
– integer
– accessible by all clients of the server
CS 360 – Spring 2007
Pacific University
Suggested Road Map
1)
2)
3)
4)
Convert Project #1 to TCP
Add the calculation stream
Add named values
Add threads to the server
•
Plan ahead!
–
–
–
–
–
think about threads as you work with the server
build a nice data structure in step three
use mutexes efficiently in step 4
commit to Subversion often!
I will be checking through your repository
•
name your project PUNetID_cs36007_PA3
– Start Early!
CS 360 – Spring 2007
Pacific University