TCPecho.rar_in

#include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> /*struct hostent & struct servent ion this header file*/ #include <stdio.h> #include <errno.h> #define LINELEN 128 /*------------------------------------------------------------------------ * main - TCP client for echo service *------------------------------------------------------------------------ */ int main(int argc, char *argv[]) { char* host = "127.0.0.1"; char* service = "echo"; char buf[LINELEN+1]; int s, n; struct hostent* phe; struct servent* pse; struct sockaddr_in sin; int outchars, inchars; /* characters sent and received */ switch (argc) { case 1: host = "127.0.0.1"; break; case 2: host = argv[1]; break; case 3: host = argv[1]; service = argv[2]; break; /* FALL THROUGH */ default: printf("usage: TCPecho [host [port]]\n"); exit(1); } memset(&sin, 0, sizeof(sin)); sin.sin_family = AF_INET; /* Map host name to IP address, allowing for dotted decimal */ phe = gethostbyname(host); if(phe) memcpy(&sin.sin_addr, phe->h_addr, phe->h_length); else if ( (sin.sin_addr.s_addr = inet_addr(host)) == INADDR_NONE ){ printf("can't get \"%s\" host entry\n", host); exit(1); } /* Map service name to port number */ if ( pse = getservbyname(service, "TCP")) sin.sin_port = pse->s_port; else if ((sin.sin_port=htons((unsigned short)atoi(service))) == 0){ printf("can't get \"%s\" service entry\n", service); exit(1); } /* Allocate a socket */ s = socket(PF_INET, SOCK_STREAM, 0); if (s < 0){ printf("can't create socket: %s\n", strerror(errno)); exit(1); } /* Connect the socket */ if (connect(s, (struct sockaddr *)&sin, sizeof(sin)) < 0){ printf("can't connect to %s.%s: %s\n", host, service,strerror(errno)); exit(1); } while (fgets(buf, sizeof(buf), stdin)) { outchars = strlen(buf); write(s, buf, outchars); /* read it back */ for (inchars = 0; inchars < outchars; inchars+=n ) { n = read(s, &buf[inchars], outchars - inchars); if (n < 0){ printf("socket read failed: %s\n", strerror(errno)); exit(1); } } fputs(buf, stdout); } close(s); exit(0); }