TCP的socket连接示例

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 :)

/* * 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)#endifchar 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 - SOCKETsec - timeout secondsusec - timeout microsecondsx - 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 WIN32char *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;}#elseextern 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[n] = '/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;}< type="text/javascript">

同时mark几个有用的url:

http://people.web.psi.ch/rohrer_u/sample1.htm   Demo program for remote CAMAC access via TCP/IP

http://www.lsword.net/code/list.asp?id=1383  将Socket应用程序从Unix向Windows移植中应注意的几点问题

引用:http://www.zeali.net/entry/13