TCP的socket连接示例(linux&windows)

Made In Zeal 转载请保留原始链接：http://www.zeali.net/entry/13

用C实现的TCP socket连接/读/写操作。采用fcntl设置非阻塞式连接以实现connect超时处理；采用select方法来设置socket读写超时。此示例可被编译运行于Windows/unix系统。

源文件connector.c

原来的代码在windows下编译不通过，今天qzj问起才发现。因为加了异步的处理，没有对这部分代码进行兼容性处理。本着做学问一丝不苟嘀精神，重新修改了一下源代码。以下代码在VC++6和linux下编译执行通过 :)

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/*

* on Unix:

* cc -c connector.c

* cc -o connector connector.o

*

* on Windows NT:

* open connector.c in Visual Studio

* press 'F7' to link -- a project to be created

* add wsock32.lib to the link section under project setting

* press 'F7' again

*

* running:

* type 'connector' for usage

*/

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <stdarg.h>

#include <errno.h>

#include <fcntl.h>

#ifdef WIN32

#include <winsock2.h>

#else

#include <unistd.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <sys/ioctl.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <netdb.h>

#endif

#ifndef INADDR_NONE

#define INADDR_NONE 0xffffffff

#endif

#define MAX_STRING_LEN 1024

#define BUFSIZE 2048

#ifndef WIN32

#define SOCKET int

#else

#define errno WSAGetLastError()

#define close(a) closesocket(a)

#define write(a, b, c) send(a, b, c, 0)

#define read(a, b, c) recv(a, b, c, 0)

#endif

char buf[BUFSIZE];

static char i_host[MAX_STRING_LEN]; /* site name */

static char i_port[MAX_STRING_LEN]; /* port number */

void err_doit(int errnoflag, const char *fmt, va_list ap);

void err_quit(const char *fmt, ...);

int tcp_connect(const char *host, const unsigned short port);

void print_usage();

//xnet_select x defines

#define READ_STATUS 0

#define WRITE_STATUS 1

#define EXCPT_STATUS 2

/*

s - SOCKET

sec - timeout seconds

usec - timeout microseconds

x - select status

*/

SOCKET xnet_select(SOCKET s, int sec, int usec, short x)

{

int st = errno;

struct timeval to;

fd_set fs;

to.tv_sec = sec;

to.tv_usec = usec;

FD_ZERO(&fs);

FD_SET(s, &fs);

switch(x){

case READ_STATUS:

st = select(s+1, &fs, 0, 0, &to);

break;

case WRITE_STATUS:

st = select(s+1, 0, &fs, 0, &to);

break;

case EXCPT_STATUS:

st = select(s+1, 0, 0, &fs, &to);

break;

}

return(st);

}

int tcp_connect(const char *host, const unsigned short port)

{

unsigned long non_blocking = 1;

unsigned long blocking = 0;

int ret = 0;

char * transport = "tcp";

struct hostent *phe; /* pointer to host information entry */

struct protoent *ppe; /* pointer to protocol information entry*/

struct sockaddr_in sin; /* an Internet endpoint address */

SOCKET s; /* socket descriptor and socket type */

int error;

#ifdef WIN32

{

WORD wVersionRequested;

WSADATA wsaData;

int err;

wVersionRequested = MAKEWORD( 2, 0 );

err = WSAStartup( wVersionRequested, &wsaData );

if ( err != 0 ) {

/* Tell the user that we couldn't find a usable */

/* WinSock DLL. */

printf("can't initialize socket library/n");

exit(0);

}

}

#endif

memset(&sin, 0, sizeof(sin));

sin.sin_family = AF_INET;

if ((sin.sin_port = htons(port)) == 0)

err_quit("invalid port /"%d/"/n", port);

/* Map host name to IP address, allowing for dotted decimal */

if ( phe = gethostbyname(host) )

memcpy(&sin.sin_addr, phe->h_addr, phe->h_length);

else if ( (sin.sin_addr.s_addr = inet_addr(host)) == INADDR_NONE )

err_quit("can't get /"%s/" host entry/n", host);

/* Map transport protocol name to protocol number */

if ( (ppe = getprotobyname(transport)) == 0)

err_quit("can't get /"%s/" protocol entry/n", transport);

/* Allocate a socket */

s = socket(PF_INET, SOCK_STREAM, ppe->p_proto);

if (s < 0)

err_quit("can't create socket: %s/n", strerror(errno));

/* Connect the socket with timeout */

#ifdef WIN32

ioctlsocket(s,FIONBIO,&non_blocking);

#else

ioctl(s,FIONBIO,&non_blocking);

#endif

//fcntl(s,F_SETFL, O_NONBLOCK);

if (connect(s, (struct sockaddr *)&sin, sizeof(sin)) == -1){

struct timeval tv;

fd_set writefds;

// 设置连接超时时间

tv.tv_sec = 10; // 秒数

tv.tv_usec = 0; // 毫秒

FD_ZERO(&writefds);

FD_SET(s, &writefds);

if(select(s+1,NULL,&writefds,NULL,&tv) != 0){

if(FD_ISSET(s,&writefds)){

int len=sizeof(error);

//下面的一句一定要，主要针对防火墙

if(getsockopt(s, SOL_SOCKET, SO_ERROR, (char *)&error, &len) < 0)

goto error_ret;

if(error != 0)

goto error_ret;

}

else

goto error_ret; //timeout or error happen

}

else goto error_ret; ;

#ifdef WIN32

ioctlsocket(s,FIONBIO,&blocking);

#else

ioctl(s,FIONBIO,&blocking);

#endif

}

else{

error_ret:

close(s);

err_quit("can't connect to %s:%d/n", host, port);

}

return s;

}

void err_doit(int errnoflag, const char *fmt, va_list ap)

{

int errno_save;

char buf[MAX_STRING_LEN];

errno_save = errno;

vsprintf(buf, fmt, ap);

if (errnoflag)

sprintf(buf + strlen(buf), ": %s", strerror(errno_save));

strcat(buf, "/n");

fflush(stdout);

fputs(buf, stderr);

fflush(NULL);

return;

}

/* Print a message and terminate. */

void err_quit(const char *fmt, ...)

{

va_list ap;

va_start(ap, fmt);

err_doit(0, fmt, ap);

va_end(ap);

exit(1);

}

#ifdef WIN32

char *optarg;

char getopt(int c, char *v[], char *opts)

{

static int now = 1;

char *p;

if (now >= c) return EOF;

if (v[now][0] == '-' && (p = strchr(opts, v[now][1]))) {

optarg = v[now+1];

now +=2;

return *p;

}

return EOF;

}

#else

extern char *optarg;

#endif

#define required(a) if (!a) { return -1; }

int init(int argc, char *argv[])

{

char c;

//int i,optlen;

//int slashcnt;

i_host[0] = '/0';

i_port[0] = '/0';

while ((c = getopt(argc, argv, "h:p:?")) != EOF) {

if (c == '?')

return -1;

switch (c) {

case 'h':

required(optarg);

strcpy(i_host, optarg);

break;

case 'p':

required(optarg);

strcpy(i_port, optarg);

break;

default:

return -1;

}

}

/*

* there is no default value for hostname, port number,

* password or uri

*/

if (i_host[0] == '/0' || i_port[0] == '/0')

return -1;

return 1;

}

void print_usage()

{

char *usage[] =

{

"Usage:",

" -h host name",

" -p port",

"example:",

" -h 127.0.0.1 -p 4001",

};

int i;

for (i = 0; i < sizeof(usage) / sizeof(char*); i++)

printf("%s/n", usage[i]);

return;

}

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

{

SOCKET fd;

int n;

/* parse command line etc ... */

if (init(argc, argv) < 0) {

print_usage();

exit(1);

}

buf[0] = '/0';

/* pack the info into the buffer */

strcpy(buf, "HelloWorld");

/* make connection to the server */

fd = tcp_connect(i_host, (unsigned short)atoi(i_port));

if(xnet_select(fd, 0, 500, WRITE_STATUS)>0){

/* send off the message */

write(fd, buf, strlen(buf));

}

else{

err_quit("Socket I/O Write Timeout %s:%s/n", i_host, i_port);

}

if(xnet_select(fd, 3, 0, READ_STATUS)>0){

/* display the server response */

printf("Server response:/n");

n = read(fd, buf, BUFSIZE);

buf
= '/0';

printf("%s/n", buf);

}

else{

err_quit("Socket I/O Read Timeout %s:%s/n", i_host, i_port);

}

close(fd);

#ifdef WIN32

WSACleanup();

#endif

return 0;

}