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if(FD_ISSET(STDIN_FILENO, &rset)) { if((n=read(STDIN_FILENO, toiptr, &to[MAXLINE]-toiptr))<0) { if(errno!=EWOULDBLOCK) err_sys("read...

#include "unp.h"void str_client(FILE *fp, int sockfd){ pid_t pid; char sendline[MAXLINE], recvline[MAXLINE]; if((pid=Fork())==0) { while(Readline(socfd, recvline, MAXLINE)&...

在这里插入代码片str_echo function: asks for client’s credentials

Receiving Sender CredentialsIn Figure 14.13(See 9.3.6), we showed another type of data that can be passed along a Unix domain socket as ancillary data: user credentials. Exactly how credentials are p...

#include "unp.h"ssize_t read_fd(int fd, void *ptr, size_t nbytes, int *recvfd){ struct msghdr msg; struct iovec iov[1]; ssize_t n;#ifdef HAVE_MSGHDR_MSG_CONTROL union{ str...

#include "unp.h"int my_open(const char *, int);int main(int argc, char **argv){ int fd, n; char buff[BUFFSIZE]; if(argc!=2) err_quit("usage: mycat <pathname>"); ...

Unix Domain Datagram Client/Server#include "unp.h"int main(int argc, char **argv){ int sockfd; struct sockaddr_un servaddr; sockfd=Socket(AF_LOCAL, SOCK_STREAM,0); bzero(&ser...

‘socketpair’ FunctionThe socketpair function creates two sockets that are then connected together. This function applies only to Unix domain sockets.#include <sys/socket.h>int socketpair(int ...

Unix Domain ProtocolsIntroductionThe Unix domain protocols are not an actual protocol suite, but a way of performing client/server communication on a single host using the same API that is used for ...

The kqueue interface includes the following two functions and macro:#include <sys/types.h>#include <sys/event.h>#include <sys/time.h>int kqueue(void);int kevent(int kq, const st...

The difference between CMSG_LEN and CMSG_SPACE is that the former does not account for any padding following the data portion of the ancillary data object and is therefore the value to store in cmsg_l...

The problem here is the buffering performed automatically by the standard I/O library on the server. There are three types of buffering performed by the standard I/O library:1.Fully buffered means th...

Both functions package most arguments into a msghdr structure.struct msghdr { void *msg_name; /* protocol address */ socklen_t msg_namelen; /* size of protocol address */ struct iovec *msg_iov; /*...

#include "unp.h"int readable_timeo(int fd, int second){ fd_set rset; struct timeval tv; FD_ZERO(&rset); FD_SET(fd, &rset); tv.tv_sec=second; t

Advanced I/O FunctionsIntroductionThis chapter covers a variety of functions and techniques that we lump into the category of “advanced I/O.” First is setting a timeout on an I/O operation, which ca...

‘inetd’ DaemonOn a typical Unix system, there could be many servers in existence, just waiting for a client request to arrive. Examples are FTP, Telnet, Rlogin, TFTP, and so on. With systems before 4...

‘daemon_init’ FunctionFigure 13.4 shows a function named daemon_init that we can call (normally from a server) to daemonize the process. This function should be suitable for use on all variants of Un...

Source Code PortabilityMost existing network applications are written assuming IPv4. sockaddr_in structures are allocated and filled in and the calls to socket specify AF_INET as the first argument. ...

‘gethostbyname_r’ and ‘gethostbyaddr_r’ FunctionsThere are two ways to make a nonre-entrant function such as gethostbyname re-entrant.1.Instead of filling in and returning a static structure, the ca...

#include "unp.h"#include <time.h>int main(int argc, char **argv){ int sockfd; ssize_t n; char buff[MAXLINE]; time_t ticks; socklen_t len; struct sockaddr_storage clie...

#include "unp.h"int main(int argc, char **argv){ int sockfd, n; char recvline[MAXLINE+1]; socklen_t salen; struct sockaddr *sa; if(argc!=3) err_quit("usage: daytimeudpc...

#include "unp.h"#include <time.h>int main(int argc, char **argv){ int listenfd, connfd; socklen_t len; char buff[MAXLINE]; time_t ticks; strct sockaddr_storage clientaddr...

#include "unp.h"int tcp_listen(const char *host, const char *serv, socklen_t *addrlenp){ int listenfd, n; const int on=1; struct addrinfo hints, res, &ressave; bzero(&hints...

‘tcp_connect’ FunctionWe will now write two functions that use getaddrinfo to handle most scenarios for the TCP clients and servers that we write. The first function, tcp_connect, performs the nor...

‘gai_strerror’ FunctionThe nonzero error return values from getaddrinfo have the names and meanings shown in Figure 11.7. The function gai_strerror takes one of these values as an argument and retur...

‘getaddrinfo’ FunctionThe gethostbyname and gethostbyaddr functions only support IPv4. The API for resolving IPv6 addresses went through several iterations, as will be described in Section 11.20(See...

‘gethostbyaddr’ FunctionThe function gethostbyaddr takes a binary IPv4 address and tries to find the hostname corresponding to that address. This is the reverse of gethostbyname.#include <netdb...

We encourage the use of getaddrinfo (Section 11.6(See 8.9.6)) in new programs.#include <netdb.h>struct hostent *gethostbyname (const char *hostname);The non-null pointer returned by this ...

Controlling Terminationfor(;;){ len=sizeof(struct sockaddr_in); rd_sz=Sctp_recvmsg(sock_fd, readbuf, sizeof(readbuf), (SA *)&cliaddr, &len, &sri, &msg_flags); if(strea...

SCTP One-to-Many-Style Streaming Echo Client: ‘main’ Function#include "unp.h"int main(int argc, char **argv){ int sock_fd; struct sockaddr_in servaddr; struct sctp_event_subscribe e...

ssf_flags will be set to one of two values:SCTP_DATA_UNSENT, which indicates that the message could never be transmitted to the peer (e.g., flow control prevented the message from being sent before...

SCTP One-to-Many-Style Streaming Echo Server: ‘main’ Function#include "unp.h"int main(int argc, char **argv){ int sock_fd, msg_flags; char readbuf[BUFFSZIE]; struct sockaddr_in serv...

‘sctp_opt_info’ FunctionThe sctp_opt_info function is provided for implementations that cannot use the getsockopt functions for SCTP. This inability to use the getsockopt function is because some of...

With SCTP, a one-to-many socket can also be used in conjunction with the sctp_peeloff function (see Section 9.12(See 8.7.12)) to allow the iterative and concurrent server models to be combined as foll...

Elementary SCTP SocketsIntroductionSCTP is a newer transport protocol, standardized in the IETF in 2000 (compared with TCP, which was standardized in 1981). It was first designed to meet the needs...

include "unp.h"static void recvfrom_int(int);static int count;void dg_echo(int sockfd, SA *pclientaddr, socklen_t clientlne){ int n; socklen_t len; char mesg[MAXLINE]; Singal(SI...

PerformanceWhen an application calls sendto on an unconnected UDP socket, Berkeley-derived kernels temporarily connect the socket, send the datagram, and then unconnect the socket (pp. 762–763 of TC...

Lost DatagramsOur UDP client/server example is not reliable. If a client datagram is lost (say it is discarded by some router between the client and server), the client will block forever in its cal...

#include "unp.h"int main(int argc, char **argv){ int sockfd; struct sockaddr_in servaddr, cliaddr; sockfd=Socket(AF_INET, SOCK_DGRAM,0); bzero(&servaddr, sizeof(servaddr)); ...

‘fcntl’ Functionfcntl stands for “file control” and this function performs various descriptor control operations. Before describing the function and how it affects a socket, we need to look at the...