CH4b数据通信--网络程序.ppt

1、数字通信(实训)之,客户机与服务器 的实用程序,程序功能,Client acquires user information from Remote server Client is a program that can be called on by user with Remote hostname and username info wanted,客户机,/client.cpp #include # include # include /A application client prog supporting whois service main(int argc, char*argv);

2、 int s;/socket descriptor int len;/received data length struct sockaddr_in sa;/internet socket address struct hostent *hp;/host name lookup result; struct servent *sp;/service lookup,客户机,char bufBUFSIZ+1; char *myname,*host,*user;/prog name,remote user and host name myname=argv0; if (argc!=3) exit(1

3、);/usage:progname host,user host=argv1; user=argv2; /lookup hostname if(hp=gethostname(host)=NULL) /Get a 32bites IP address of host devided by points and decimal numbers exit(1);/no result /hosts address and type is put into socket struct bcopy(char *)hp-h_addr, (char *) /look up socket number for

4、service,客户机,if (sp=getservbyname(“whois”,”tcp”)=NULL) /get port number exit(1);/no whois service on the host /put the whois socket No. into socket structure sa.sin_port=sp-s_port; /allocate socket if(s=socket(hp-h_addesstype,SOCK_STREAM,0)0) exit(1); /connect to the remote server if(connect(s, /send

5、ing request,客户机,if(write(s,user,strlen(user)!=strlen(user) exit(3); /reading reply while(len=read(s,buf,BUFSIZ)0) write(s,buf,len); close(s);exit(0); ,服务器,在端口上监听并返回信息 /server.cpp #include # include # include #include # include # include /use:whois hostname,username,port43 #define BACKLOC 5 /queuing

6、No. #define MAXHOSTNAME 32 /maximum name len main(argc,argv),服务器, int argc; char*argv; int s,t;/socket descriptors int i; struct sockaddr_in sa,isa;/internet socket address struct hostent *hp;/host name lookup result; struct servent *sp;/service lookup char *myname;/prog name char localhostMAXHOSTNA

7、ME+1; myname=argv0; /look up service entry if(sp=getservbyname(“whois”,”TCP”)=NULL) exit(1);/no this service,服务器,/get host info if(hp=gethostname(localhost, MAXHOSTNAME)=NULL) exit(1); /put socket no and addr info into socket structure sa.sin_port=sp-s_port; bcopy(char *)hp-h_addr, (char *) /setting maximum connections ,s:service port listen(s,BACKLOG)；/ BACKLOG is the maxmum queue len received while(1) /waiting for connection,服务器