connection speed - Page 541

Java. Read file from FTP but DONT download it whole

- by Alexey

I need to read CSV file header from FTP. As these files can be very huge, I dont need to donwload them. Is there a way to read first line of CSV file from FTP and abort connection?

C socket programming: select() is returning 0 despite messages sent from server

Hey all, I'm using select() to recv() messages from server, using TCP/IP. When I send() messages from the server, it returns a reasonable number of bytes, saying it's sent successful. And it does get to the client successfully when I use while loop to just recv(). Everything is fine and dandy. while(1) recv() // obviously pseudocode However, when I try to use select(), select() returns 0 from timeout (which is set to 1 second) and for the life of me I cannot figure out why it doesn't see the messages sent from the server. I should also mention that when the server disconnects, select() doesn't see that either, where as if I were to use recv(), it would return 0 to indicate that the connection using the socket has been closed. Any inputs or thoughts are deeply appreciated. #include <arpa/inet.h> #include <errno.h> #include <fcntl.h> #include <netdb.h> #include <netinet/in.h> #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <strings.h> #include <sys/select.h> #include <sys/socket.h> #include <sys/time.h> #include <sys/types.h> #include <time.h> #include <unistd.h> #define SERVER_PORT 10000 #define MAX_CONNECTION 20 #define MAX_MSG 50 struct client { char c_name[MAX_MSG]; char g_name[MAX_MSG]; int csock; int host; // 0 = not host of a multicast group struct sockaddr_in client_address; struct client * next_host; struct client * next_client; }; struct fd_info { char c_name[MAX_MSG]; int socks_inuse[MAX_CONNECTION]; int sock_fd, max_fd; int exit; struct client * c_sys; struct sockaddr_in c_address[MAX_CONNECTION]; struct sockaddr_in server_address; struct sockaddr_in client_address; fd_set read_set; }; struct message { char c_name[MAX_MSG]; char g_name[MAX_MSG]; char _command[3][MAX_MSG]; char _payload[MAX_MSG]; struct sockaddr_in client_address; struct client peer; }; int main(int argc, char * argv[]) { char * host; char * temp; int i, sockfd; int msg_len, rv, ready; int connection, management, socketread; int sockfds[MAX_CONNECTION]; // for three threads that handle new connections, user inputs and select() for sockets pthread_t connection_handler, manager, socket_reader; struct sockaddr_in server_address, client_address; struct hostent * hserver, cserver; struct timeval timeout; struct message msg; struct fd_info info; info.exit = 0; // exit information: if exit = 1, threads quit info.c_sys = NULL; // looking up from the host database if (argc == 3) { host = argv[1]; // server address strncpy(info.c_name, argv[2], strlen(argv[2])); // client name } else { printf("plz read the manual, kthxbai\n"); exit(1); } printf("host is %s and hp is %p\n", host, hserver); hserver = gethostbyname(host); if (hserver) { printf("host found: %s\n", hserver->h_name ); } else { printf("host not found\n"); exit(1); } // setting up address and port structure information on serverside bzero((char * ) &server_address, sizeof(server_address)); // copy zeroes into string server_address.sin_family = AF_INET; memcpy(&server_address.sin_addr, hserver->h_addr, hserver->h_length); server_address.sin_port = htons(SERVER_PORT); bzero((char * ) &client_address, sizeof(client_address)); // copy zeroes into string client_address.sin_family = AF_INET; client_address.sin_addr.s_addr = htonl(INADDR_ANY); client_address.sin_port = htons(SERVER_PORT); // opening up socket sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) exit(1); else { printf("socket is opened: %i \n", sockfd); info.sock_fd = sockfd; } // sets up time out option for the bound socket timeout.tv_sec = 1; // seconds timeout.tv_usec = 0; // micro seconds ( 0.5 seconds) setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(struct timeval)); // binding socket to a port rv = bind(sockfd, (struct sockaddr *) &client_address, sizeof(client_address)); if (rv < 0) { printf("MAIN: ERROR bind() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("socket is bound\n"); printf("MAIN: %li \n", client_address.sin_addr.s_addr); // connecting rv = connect(sockfd, (struct sockaddr *) &server_address, sizeof(server_address)); info.server_address = server_address; info.client_address = client_address; info.sock_fd = sockfd; info.max_fd = sockfd; printf("rv = %i\n", rv); if (rv < 0) { printf("MAIN: ERROR connect() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("connected\n"); fd_set readset; FD_ZERO(&readset); FD_ZERO(&info.read_set); FD_SET(info.sock_fd, &info.read_set); while(1) { readset = info.read_set; printf("MAIN: %i \n", readset); ready = select((info.max_fd)+1, &readset, NULL, NULL, &timeout); if(ready == -1) { sleep(2); printf("TEST: MAIN: ready = -1. %s \n", strerror(errno)); } else if (ready == 0) { sleep(2); printf("TEST: MAIN: ready = 0. %s \n", strerror(errno)); } else if (ready > 0) { printf("TEST: MAIN: ready = %i. %s at socket %i \n", ready, strerror(errno), i); for(i = 0; i < ((info.max_fd)+1); i++) { if(FD_ISSET(i, &readset)) { rv = recv(sockfd, &msg, 500, 0); if(rv < 0) continue; else if(rv > 0) printf("MAIN: TEST: %s %s \n", msg._command[0], msg._payload); else if (rv == 0) { sleep(3); printf("MAIN: TEST: SOCKET CLOSEDDDDDD \n"); } FD_CLR(i, &readset); } } } info.read_set = readset; } // close connection close(sockfd); printf("socket closed. BYE! \n"); return(0); }

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