Socket Programming in C: The first accept() always gives me address filled with 0s

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

int main(){
    struct sockaddr_in svraddr;
    int clisock;
    pid_t pid;
    ssize_t nlen;
    struct sockaddr_in cliaddr;
    socklen_t cliaddrlen = sizeof(sockaddr_in);
    char buf[BUFSIZ];
    svraddr.sin_family=AF_INET;
    svra开发者_开发知识库ddr.sin_port=htons(49510);
    svraddr.sin_addr.s_addr=htonl(INADDR_ANY);
    int serversock = socket(PF_INET,SOCK_STREAM,0);
    if(serversock==-1){
        perror("socket()");
        exit(1);
    }
    if(bind(serversock,(struct sockaddr*)&svraddr,sizeof(svraddr))==-1){
        perror("bind()");exit(1);
    }
    if(listen(serversock,10)==-1){
        perror("listen()");exit(1);
    }
    while(1){
        clisock = accept(serversock,(struct sockaddr*)&cliaddr,&cliaddrlen);
        switch(pid=fork()){
            case -1:
            perror("fork()");exit(1);
            case 0:
            close(serversock);
            printf("CONN: client %s:%d\n",inet_ntoa(cliaddr.sin_addr),ntohs(cliaddr.sin_port));
            while((nlen=read(clisock,buf,BUFSIZ))!=0){
                perror("read");
                printf("RECV: srcport %d, %s\n",ntohs(cliaddr.sin_port),buf);
                write(clisock,"received successfully",22);
            }
            close(clisock);
            printf("DISCONN: client %d disconnected\n",ntohs(cliaddr.sin_port));
            exit(0);
            break;
            default:
            close(clisock);
        }
    }
}

Above is the entire codes for server. It is simple multiprocess based server.

what I understood is : accept() should give client address into cliaddr. it does, but it doesn't for the first one.

but strangely, Socket I/O works well.

the code is written from scratch. What did I do wrong with this?

I tried initializing cliaddr with memset, no luck.

output for server is:

CONN: client 0.0.0.0:0
DISCONN: client 0 disconnected
CONN: client 127.0.0.1:57078
DISCONN: client 57078 disconnected

accept() should always gives correct client address anytime.

Never mind. I've figure out why.

socklen_t cliaddrlen = sizeof(sockaddr_in);
=>
socklen_t cliaddrlen = sizeof(struct sockaddr_in);

I don't understand why this code's been successfully compiled. but yes, my mistake. now it works like charm.