Microsoft PowerPoint - Socket programming.ppt [相容模式]

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1 Basic Concept of Socket Socket programming 位於傳輸層和應用層之間 socket 是一種可做雙向資料傳輸的通道讓應用層可以傳送資料給 socket, 或是從 socket 接收資料 Jimmy 2011/3/29 Concept of Socket Relation between Socket and Application Socket 的概念和檔案代碼觀念相似, 一個 Socket 就是一個通訊點, 以一個整數來表示之 Socket 並不是 TCP 或 UDP 的 port number Socket 只是一個代碼代表網路協定中的一組資料 TCP 連線中雙方的 IP 位址目前連線的狀態應用程式 1 應用程式 2 應用程式 3 應用程式 4 Socket API TCP/IP 作業系統 3 網路卡

2 Socket Descriptor Concept of Port Numbers Socket( 整數 ) Port numbers are used to identify entities on a host Port numbers can be Well-known (port ) Dynamic or private (port ) Servers usually use well-known ports Any client can identify the server/service HTTP = 80, FTP = 21, Telnet = 23,... Clients usually use dynamic ports Assigned by the kernel at run time NTP daemon TCP/UDP IP Web server port 123 port 80 Ethernet Adapter 5 Server and Client Transmission Control Protocol (TCP) Server and Client exchange messages over the network through a common Socket API Server ports Clients user space TCP Reliable guarantee delivery Byte stream in-order delivery Connection-oriented single socket per connection Setup connection followed by data transfer Telephone Call Guaranteed delivery In-order delivery Connection-oriented Setup connection followed by conversation TCP/UDP Socket API TCP/UDP kernel space IP Ethernet Adapter IP Ethernet Adapter hardware Example TCP applications Web, , Telnet

3 User Datagram Protocol (UDP) TCP vs UDP UDP Single socket to receive messages No guarantee of delivery Not necessarily in-order delivery Datagram independent packets Must address each packet Postal Mail Single mailbox to receive letters Unreliable Not necessarily in-order delivery Letters sent independently Must address each reply Transmission Control Protocol (TCP) One-to-one Connection-oriented Reliable In-order delivery Transmission after Connect User Datagram Protocol (UDP) One-to-one or one-to many Connectionless Unreliable Unordered delivery Transmission with destination address Example UDP applications Multimedia, voice over IP Socket API Server Socket API Client socket 建立 socket bind 設定 socket 所使用的 local IP 及通訊埠 listen 設定 socket 等待 client 的連結請求 accept 接受來自 client 的連結請求, 並建立 socket 連結 read (TCP) 接收來自 client 所傳的資料 write (TCP) 傳送資料到 client close 結束連線 socket 建立 socket connect 建立與 server 端 socket 連線 read (TCP) 接收來自 server 所傳的資料 write (TCP) 傳送資料到 server close 結束連線 11 12

4 TCP Client-Server Interaction Network Addressing TCP Client socket() connect() connection establishment data request data reply TCP Server socket() bind() listen() accept() ext.417 Telephone Call Professors at NTU Extension Telephone No Central Number Exchange Area Code ext.315 Network Programming Applications/Servers Web Port 80 Port No. IP Address Network No. Host Number Mail Port 25 close() end-of-file notification close() Students Clients Internet domain socket 的定址結構可用來儲存 IP 位址通訊埠等訊息 IPv4 Addressing Data Structure #include <netinet/in.h> /* Internet address structure */ struct in_addr { u_long s_addr; /* 32-bit IPv4 address */ ; /* Socket address, Internet style. */ struct sockaddr_in { u_char sin_family; /* Address Family (AF_INET)*/ u_short sin_port; /* UDP or TCP Port# */ struct in_addr sin_addr; /* Internet Address */ ; 用來存放 IP 位址的 s_addr 是一個 32 位元 unsigned integer, 但是 ip 通常會表示為 xxx.xxx.xxx.xxx, 例如可使用 inet_addr() 位址轉換函數將轉換為 s_addr 所要的 32 位元 unsigned integer

5 inet_addr() Byte Ordering Functions 由於 inet_addr() 位址轉換函數將 xxx.xxx.xxx.xxx 轉換為 s_addr 所要的 32 位元 unsigned integer #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> unsigned long inet_addr(const char *string); String (ip string, ie: xxx.xxx.xxx.xxx) 由於不同的 CPU 在儲存 32 位元整數時, 會將 4 個位元組由高到低 ( 例 :motorola CPU), 或由低到高 ( 例 :intel CPU) 儲存, 造成網路處理上的錯誤因此在儲存 TCP/IP 的 IP/port number 時, 可以用位元排序函數來消除此問題 Big Endian Sun Solaris, PowerPC,... Little Endian i386, alpha,... Network byte order = Big Endian c[0] c[1] c[2] c[3] Byte Ordering Functions Converts between host byte order and network byte order h = host byte order n = network byte order l = long (4 bytes), converts IP addresses s = short (2 bytes), converts port numbers #include <netinet/in.h> unsigned long int htonl(unsigned long int hostlong); unsigned short int htons(unsigned short int hostshort); unsigned long int ntohl(unsigned long int netlong); unsigned short int ntohs(unsigned short int netshort); Simple Server Example socket() bind() listen() accept() open socket 由作業系統如同檔案一般取得一 Socket Descriptor, 讓 Server 端以後可使用這一代號進行接受外來 TCP 連線 bind 是指定 Server 端使用 local 的哪一 IP 及 Port 進行通訊對 Server 端而言是必需的 listen 表示讓此開啟的 Socket 進入被動模式, 配合 accept System Call 可接受外來之連線 Server 端的 accept System Call 接受 Client 之 connect System Call 完成三向交握, 並產生一新的 Descriptor, 此 Descriptor 即為與 Client 進行 I/O 的代號 read/write 針對已經 accept 產生之 Descriptor 進行 I/O 動作, 在此傳送 HTTP 的 Protocol 並得到 Server 回傳的 HTML 檔案內容等 close() close 關閉 TCP 連線, 釋放系統資源

6 Socket I/O: socket() Socket I/O: bind() if((fd = socket(af_inet, SOCK_STREAM, 0)) < 0) { perror( socket ); socket returns an integer (socket descriptor) fd < 0 indicates that an error occurred AF_INET associates a socket with the Internet protocol family SOCK_STREAM selects the TCP protocol SOCK_DRGAM selects the UDP protocol 不論是 TCP 或 UDP 作為傳輸協定, 都要透過 socket 作資料傳輸, 首要工作是先建立 socket 要建立 socket 可用 socket() 函數 struct sockaddr_in srv; /* used by bind() */ /* create the socket */ srv.sin_family = AF_INET; /* use the Internet addr family */ srv.sin_port = htons(8888); /* bind socket fd to port 8888*/ /* bind: a client may connect to any of my addresses */ srv.sin_addr.s_addr = htonl(inaddr_any); if(bind(fd, (struct sockaddr*) &srv, sizeof(srv)) < 0) { perror("bind"); INADDR_ANY-This allowed your program to work without knowing the IP address of the machine it was running on Socket I/O: listen() listen indicates that the server will accept a connection struct sockaddr_in srv; /* used by bind() */ /* 2) bind the socket to a port */ if(listen(fd, 5) < 0) { perror( listen ); Socket I/O: accept() accept blocks waiting for a connection struct sockaddr_in srv; /* used by bind() */ struct sockaddr_in cli; /* used by accept() */ int newfd; /* returned by accept() */ int cli_len = sizeof(cli); /* used by accept() */ /* 2) bind the socket to a port */ /* 3) listen on the socket */ newfd = accept(fd, (struct sockaddr*) &cli, &cli_len); if(newfd < 0) { perror("accept"); accept returns a new socket (newfd) with the same properties as the original socket (fd) newfd < 0 indicates that an error occurred

7 Socket I/O: accept() continued... 使用及來傳送與接收資料 struct sockaddr_in cli; /* used by accept() */ int newfd; /* returned by accept() */ int cli_len = sizeof(cli); /* used by accept() */ newfd = accept(fd, (struct sockaddr*) &cli, &cli_len); if(newfd < 0) { perror("accept"); How does the server know which client it is? cli.sin_addr.s_addr contains the client s IP address cli.sin_port contains the client s port number Now the server can exchange data with the client by using read and write on the descriptor newfd. Why does accept need to return a new descriptor? Socket I/O: read can be used with a socket Socket I/O: write can be used with a socket int newfd; /* socket descriptor */ char buf[512]; /* used by */ int nbytes; /* used by */ /* 2) bind the socket to a port */ /* 3) listen on the socket */ /* 4) accept the incoming connection */ if((nbytes = read(newfd, buf, sizeof(buf))) < 0) { perror( read ); nbyte > 0 (normal) nbyte = 0 (connection closed) nbyte < 0 (error) int newfd; /* socket descriptor */ char buf[512]; /* used by */ int nbytes; /* used by */ /* 2) bind the socket to a port */ /* 3) listen on the socket */ /* 4) accept the incoming connection */ if((nbytes = write(fd, buf, sizeof(buf))) < 0) { perror( write );

8 Simple Client Example Socket I/O: connect() socket() bind() connect() close() open socket 由作業系統如同檔案一般取得一 Socket Descriptor, 讓 Client 端以後可使用這一代號進行網路 I/O 讀寫 bind 是指定 Client 端使用 local ( 也就是本機 ) 的哪一 IP 及 Port 進行通訊若無指定, 則連線時由系統幫 Client 程式自動挑選合適的 IP 與 Port 因此對 Client 端而言是 Optional connect 是起始 TCP 的連線, 配合 Server 端的 accept System Call 完成三向交握, 因此於 connect 此 System Call 必需傳給予對方 Server 端的 IP 與 Port 的資訊 read/write 針對已經完成連線的 Socket Descriptor 進行 I/O 動作, 在此傳送 HTTP 的 Protocol 並得到 Server 回傳的 HTML 檔案內容等 close 關閉 TCP 連線, 釋放系統資源 connect allows a client to connect to a server... struct sockaddr_in srv; /* used by connect() */ /* create the socket */ /* connect: use the Internet address family */ srv.sin_family = AF_INET; /* connect: socket fd to port 8888 */ srv.sin_port = htons(8888); /* connect: connect to IP Address */ srv.sin_addr.s_addr = inet_addr( ); if(connect(fd, (struct sockaddr*) &srv, sizeof(srv)) < 0) { perror( connect"); Socket I/O: write can be used with a socket char buf[512]; /* used by */ int nbytes; /* used by */ /* 2) connect() to the server */ /* Example: A client could write a request to a server */ if((nbytes = write(fd, buf, sizeof(buf))) < 0) { perror( write ); Socket I/O: read can be used with a socket char buf[512]; /* used by */ int nbytes; /* used by */ /* 2) connect() to the server */ if((nbytes = read(fd, buf, sizeof(buf))) < 0) { perror( write );

設計 tcp 網路程式 Some useful function 網路程式會分成 client 端和 server 端設計 TCP client 端 1. 建立 socket( 使用 socket() 函數 ) 2. 向 server 要求連線 ( 使用 connect() 函數 ) 3. 若連線成功, 使用輸出入函數和 server 端互傳訊息 4.

9 設計 tcp 網路程式 Some useful function 網路程式會分成 client 端和 server 端設計 TCP client 端 1. 建立 socket( 使用 socket() 函數 ) 2. 向 server 要求連線 ( 使用 connect() 函數 ) 3. 若連線成功, 使用輸出入函數和 server 端互傳訊息 4. 關閉 socket, 結束連線 ( 使用 close() 函數 ) 設計 TCP server 端 1. 建立 socket( 使用 socket() 函數 ) 2. 連結 socket( 使用 bind() 函數 ) 3. 開啟 listening socket( 使用 listen() 函數 ) 4. 等待 client 連線要求 ( 使用 accept() 函數 ) 5. 若連線成功, 使用輸出入函數和 client 端互傳訊息 6. 關閉 socket, 結束連線 ( 使用 close() 函數 ) gethostbyname() get address for given host name (e.g for name cs.stanford.edu ); getservbyname() get port and protocol for a given service e.g. ftp, http (e.g. http is port 80, TCP) getsockname() get local address and local port of a socket getpeername() get remote address and remote port of a socket Hw4 Your job is to implement an Echo Server which will send back and output some information (60%) when it receives, whatever it receives You also have to write a program which will send message to the Echo Server(40%) Execution format Echo Server execution format (5%) While someone connects to the server, server should output some information EchoServer server_port Client execution format (5%) EchoClient server_ip server_port message

10 4/11 23:59 Due Reference Socket programming in C/C++ Name your program in this way Student_ID_s.c for Echo Server Student_ID_c.c for Client Make your program as a tarball or zip file tar zcvf Student_ID_hw4.tar.gz Student_ID_s.c Student_ID_c.c the file to jimmychad@gmail.com Subject: CN211 HW4 Student_ID 4/11 23:59 Due *Policy on late submission of assignment will be decided N2010/Slides/Socket_Programming_2010_1. pdf et.ppt temprogramming2010/ch07.htm

TCP/IP TCP/IP OSI IP TCP IP IP TCP/IP TCP/IP

TCP/IP : TCP/IP TCP/IP OSI IP TCP IP IP TCP/IP TCP/IP 1. ASCII EBCDIC Extended Binary-Coded Decimal Interchange Code 2. / (1) (2) Single System Image SSI) (3) I/O (4) 3.OSI OSI Open System Interconnection