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TCP

TCP. section 6.5 (Read this section!) 27 Feb 2007. 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. Socket Libraries (Unix/Linux).

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TCP

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  1. TCP section 6.5 (Read this section!) 27 Feb 2007

  2. 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

  3. 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

  4. API Usage: Call Sequences • TCP over IP (connection-based): socket() bind() listen() accept() recv()/send() close() server socket() connect() send()/recv() close() client

  5. 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

  6. 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.

  7. 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> • 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

  8. 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);

  9. 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); close(listenSock);

  10. 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

  11. Suggested Road Map • 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!

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