linux socket基础

一个简单的客户端获取服务器时间的例子：

服务器代码：

#include <iostream>
#include "unp.h"
#include "my_err.h"
#define DEFAULT_PORT 8000

int main(int argc, const char * argv[])
{

    int listenfd, connfd;
    struct sockaddr_in servaddr;
    char buff[MAXLINE];
    time_t ticks;
    listenfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(DEFAULT_PORT); //端口号

    Bind(listenfd, (SA *) &servaddr, sizeof(servaddr));

    Listen(listenfd, LISTENQ);

    for ( ; ; ){
        std::cout << "wait connect" << std::endl;
        connfd = Accept(listenfd, (SA *) NULL, NULL);
        ticks = time(NULL);
        snprintf(buff, sizeof(buff), "%.24s\r\n", ctime(&ticks));
        Write(connfd, buff, strlen(buff));

        Close(connfd);
    }
    std::cout << "Hello, World!\n";
    return 0;
}

客户端代码：

#include <iostream>
#include "unp.h"
#include "my_err.h"
int main(int argc, const char * argv[])
{
    int sockfd, n;
    char recvline[MAXLINE + 1];
    struct sockaddr_in servaddr;
//    if (argc != 2)
//        err_quit("usage: a.out <Ipaddress>");

    if ( (sockfd = Socket(AF_INET, SOCK_STREAM, 0)) <0)
        err_sys("socket error");

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(8000);
    if (inet_pton(AF_INET, "192.168.1.59", &servaddr.sin_addr) <= 0) //127.0.0.1
        err_quit("inet_pton error for %s", argv[1]);

    if (connect(sockfd, (SA *) &servaddr, sizeof(servaddr)) < 0 )
        err_sys("connect error");

    while ( (n = read(sockfd, recvline, MAXLINE)) > 0 ) {
        recvline[n] = 0;
        if (fputs(recvline , stdout) == EOF)
            err_sys("fputs error");
    }

    if (n < 0 )
        err_sys("read error");
    return 0;
}

my_err.h 文件

#ifndef time1_my_err_h
#define time1_my_err_h
#include <errno.h> /* for definition of errno */
#include <stdarg.h> /* ISO C variable aruments */

static void err_doit(int, int, const char *, va_list);

/*
 * Nonfatal error related to a system call.
 * Print a message and return.
 */
void
err_ret(const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    err_doit(1, errno, fmt, ap);
    va_end(ap);
}

/*
 * Fatal error related to a system call.
 * Print a message and terminate.
 */
void
err_sys(const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    err_doit(1, errno, fmt, ap);
    va_end(ap);
    exit(1);
}

/*
 * Fatal error unrelated to a system call.
 * Error code passed as explict parameter.
 * Print a message and terminate.
 */
void
err_exit(int error, const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    err_doit(1, error, fmt, ap);
    va_end(ap);
    exit(1);
}

/*
 * Fatal error related to a system call.
 * Print a message, dump core, and terminate.
 */
void
err_dump(const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    err_doit(1, errno, fmt, ap);
    va_end(ap);
    abort(); /* dump core and terminate */
    exit(1); /* shouldn't get here */
}

/*
 * Nonfatal error unrelated to a system call.
 * Print a message and return.
 */
void
err_msg(const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    err_doit(0, 0, fmt, ap);
    va_end(ap);
}

/*
 * Fatal error unrelated to a system call.
 * Print a message and terminate.
 */
void
err_quit(const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    err_doit(0, 0, fmt, ap);
    va_end(ap);
    exit(1);
}

/*
 * Print a message and return to caller.
 * Caller specifies "errnoflag".
 */
static void
err_doit(int errnoflag, int error, const char *fmt, va_list ap)
{
    char buf[MAXLINE];
    vsnprintf(buf, MAXLINE, fmt, ap);
    if (errnoflag)
        snprintf(buf+strlen(buf), MAXLINE-strlen(buf), ": %s",
                 strerror(error));
    strcat(buf, "\n");
    fflush(stdout); /* in case stdout and stderr are the same */
    fputs(buf, stderr);
    fflush(NULL); /* flushes all stdio output streams */
}

int
Socket(int family, int type, int protocol)
{
	int		n;

	if ( (n = socket(family, type, protocol)) < 0)
		err_sys("socket error");
	return(n);
}

void
Bind(int fd, const struct sockaddr *sa, socklen_t salen)
{
	if (bind(fd, sa, salen) < 0)
		err_sys("bind error");
}

void
Close(int fd)
{
	if (close(fd) == -1)
		err_sys("close error");
}

void
Write(int fd, void *ptr, size_t nbytes)
{
	if (write(fd, ptr, nbytes) != nbytes)
		err_sys("write error");
}

int
Accept(int fd, struct sockaddr *sa, socklen_t *salenptr)
{
	int		n;

again:
	if ( (n = accept(fd, sa, salenptr)) < 0) {
#ifdef	EPROTO
		if (errno == EPROTO || errno == ECONNABORTED)
#else
            if (errno == ECONNABORTED)
#endif
                goto again;
            else
                err_sys("accept error");
	}
	return(n);
}

void
Listen(int fd, int backlog)
{
	char	*ptr;

    /*4can override 2nd argument with environment variable */
	if ( (ptr = getenv("LISTENQ")) != NULL)
		backlog = atoi(ptr);

	if (listen(fd, backlog) < 0)
		err_sys("listen error");
}
#endif

对比 window socket    http://blog.csdn.net/tutuboke/article/details/45799667