echo_client.c

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

#define BUF_SIZE 1024
void error_handling(char *message);

int main(int argc,char *argv[]){
    int sock;
    char message[BUF_SIZE];
    struct sockaddr_in serv_addr;
    
    int str_len,recv_len,recv_cnt;

    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() error");

    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) error!");
    else
        puts("connected..........");

    while(1){
        fputs("Input message(Q to quit): ",stdout);
        fgets(message, BUF_SIZE, stdin);

        if(!strcmp(message,"q\n") || !strcmp(message,"Q\n"))
            break;
        
        str_len=write(sock, message, strlen(message));
        recv_len=0;
        while(recv_len<str_len){
            recv_cnt=0;
            while(recv_len<str_len)
            {
                recv_cnt=read(sock,&message[recv_len],BUF_SIZE-1);
                if(recv_cnt==-1)
                    error_handling("read() error!");
                recv_len+=recv_cnt;
            }
        }
        message[recv_len]=0;
        printf("Message from server: %s",message);
    }

    close(sock);
    return 0;
}

void error_handling(char *message){
    fputs(message,stderr);
    fputc('\n',stderr);
    exit(1);
}