Linux Socket Programmierung: listen() Anruf zeigt unerwartetes Verhalten

Question

Ich schrieb ein einfaches Socket-Programm für einen Server, wo ich einen Hang in listen() Anruf bekam. Überraschenderweise hängt dieses Stück Code:

if((res = listen(sockfd, 5)) == -1) 
    { 
     perror("Error in listening over socket"); 
     exit(1); 
    } 

Wie ist das möglich? Hier ist mein voller Code als Referenz:

#include <stdio.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <stdlib.h> 
#include <string.h> 
#include <unistd.h> 
#include <arpa/inet.h> 

#define MYPORT 7891 

int main() 
{ 
    int sockfd, newfd, res; 
    struct sockaddr_in my_addr, their_addr; 
    socklen_t their_addr_size; 
    char msg[100] = {'\0'}; 

    /* open a socket for the server */ 
    if((sockfd = socket(AF_INET, SOCK_STREAM,0)) == -1) 
    { 
     perror("Error opening socket"); 
     exit(1); 
    } 

    printf("Socket opened successfully\n"); 

    /* specify the interface details, where the server should listen for incoming messages. It is set by bind */ 
    my_addr.sin_family = AF_INET; 
    my_addr.sin_port = htons(MYPORT); 
    my_addr.sin_addr.s_addr = INADDR_ANY; /* listen on every interface, eth0, wlan, whatever f**kin place */ 
    memset(&(my_addr.sin_zero),0,8); 
    if((res = bind(sockfd, (struct sockaddr *)&(my_addr), sizeof(struct sockaddr_in))) == -1) 
    { 
     perror("Error while bind()"); 
     exit(1); 
    } 

    printf("Bind() is successfull\n"); 

    /* listen on the socket, setting the waiting queue size to max 5 connections. Other connections will get ECONNREFUSED error */ 
    if((res = listen(sockfd, 5)) == -1) 
    { 
     perror("Error in listening over socket"); 
     exit(1); 
    } 
    // if(listen(sockfd,5)==0) 
    // printf("Listening\n"); 
    // else 
    // printf("Error\n"); 


    printf("Listening...."); 

    /* accept incoming request */ 
    their_addr_size = sizeof(struct sockaddr_in); 
    if((newfd = accept(sockfd, (struct sockaddr *)&their_addr, &their_addr_size)) == -1) 
    { 
     perror("Error accepting connection"); 
     exit(1); 
    } 

    /* write data */ 
    printf("Enter the data to be sent\n"); 
    while(1) 
    { 
     scanf("%s",msg); 
     write(newfd, msg, strlen(msg)); 
    } 

    /* though it never comes here due to infinite while loop */ 
    close(newfd); 
    close(sockfd); 
    return 0; 
} 

Ich bekomme nicht "Listening ...".

Answer 1

Es war aufgrund der sdtout Daten gepuffert. Doing fflush(stdout), gab den richtigen Druck. Und der Prozess ist jetzt an der erwarteten Position accept() blockiert.