week2 network programming, hello server & client code

network2w_helloclient.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
 
void error_handling(char* msg);
 
int main(int argc,char* argv[])
{
    int sock;
    struct sockaddr_in serv_addr;
    char msg[30];
    int str_len;
 
    if(argc!=3)
    {
        printf("Usage : %s <IP> <port> \n",argv[0]);
        exit(1);
    }
 
    sock = socket(PF_INET,SOCK_STREAM,0);
    if(sock==-1)
        error_handling("socket() err");
 
    memset(&serv_addr,0,sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
    serv_addr.sin_port = htons(atoi(argv[2]));
 
    if(connect(sock,(struct sockaddr*)&serv_addr,sizeof(serv_addr))==-1)
        error_handling("connect() err");
 
    str_len = read(sock,msg,sizeof(msg));
    if(str_len==-1)
        error_handling("read() err");
    printf("msg from server : %s\n",msg);
    close(sock);
 
    return 0;
}
 
void error_handling(char* msg)
{
    fputs(msg,stderr);
    fputs('\n',stderr);
    exit(1);
}

network2w_helloserver.c

/*
2 weeks server code
server, tcp
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
 
void error_handling(char* msg);
 
int main(int argc,char* argv[])
{
    int serv_sock;
    int clnt_sock;
 
    struct sockaddr_in serv_addr;
    struct sockaddr_in clnt_addr;
    socklen_t clnt_addr_size;
 
    char msg[]="hello world";
 
    if(argc!=2)
    {
        printf("Usage : %s<port>\n",argv[0]);
        exit(1);
    }
 
    serv_sock = socket(PF_INET,SOCK_STREAM,0);
    if(serv_sock==-1)
        error_handling("socket() err");
    memset(&serv_addr,0,sizeof(serv_addr));
    serv_addr.sin_family=AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(atoi(argv[1]));
 
    if(bind(serv_sock,(struct sockaddr*)&serv_addr,sizeof(serv_addr))==-1)
        error_handling("bind() err");
    if(listen(serv_sock,5)==-1)
        error_handling("listen() err");
    clnt_addr_size = sizeof(clnt_addr);
    clnt_sock = accept(serv_sock,(struct sockaddr*)&clnt_addr,&clnt_addr_size);
    if(clnt_sock==-1)
        error_handling("accept err");
    write(clnt_sock,msg,sizeof(msg));
    close(clnt_sock);
    close(serv_sock);
    return 0;
}
 
void error_handling(char* msg)
{
    fputs(msg,stderr);
    fputs('\n',stderr);
    exit(1);
}