c언어 tcp소켓 코딩 좀 알려주세요...

(server)
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>    	/* close(), write(), read() */
#include <arpa/inet.h> 	/* socket(), bind(), listen(), accept(), connect() 	*/
#include <sys/socket.h>	/*													*/
#include <sys/types.h>	/*											open() 	*/
#include <sys/stat.h> 
#include <fcntl.h>
#include <signal.h>
#include <sys/wait.h>
#include <time.h>
#include <sys/sem.h>
#include <malloc.h>
 
#define INITCHAR(x) memset(x,0x00,sizeof(x))
#define PORT 2100      /* 포트 번호 고정 */
#define BUFSIZE 1024
 
EXEC SQL INCLUDE SQLCA;
 
void error_handling(char *message);
void z_handler(int sig);
int echo_serv(int clnt_sock);
 
int main(int argc, char **argv)
{
	int clnt_len;
 	int serv_sock;
  	int clnt_sock;
  	struct sockaddr_in serv_addr;
  	struct sockaddr_in clnt_addr;
  	time_t s_time;
  	char a[100],b[100];
  	int addr_size, str_len, state;
  	pid_t pid;
  	char message[BUFSIZE];
  	struct sigaction act;
  	act.sa_handler=z_handler;
  	sigemptyset(&act.sa_mask);
  	act.sa_flags=0;
 
  	Connect_Oracle();
 	daemon_init(); /* 데몬 */  
 
 	state=sigaction(SIGCHLD, &act, 0); /* 시그널 핸들러 등록 */
	if(state != 0){
		puts("sigaction() error");
		exit(1);
  	} 	
  	serv_sock=socket(PF_INET, SOCK_STREAM, 0);   
  	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(PORT);
 
  	if(bind(serv_sock, (struct sockaddr*) &serv_addr, sizeof(serv_addr))==-1)
  		error_handling("bind() error");
 
  	if(listen(serv_sock, 5)==-1)
    	error_handling("listen() error");
 
	for(;;){
		clnt_len = sizeof(clnt_addr);
		clnt_sock=accept(serv_sock,(struct sockaddr*)&clnt_addr,&clnt_len);
		if(serv_sock == -1){
			error_handling("accept() error");
		}
		fflush(stdout);
		pid = fork();
		if (pid < 0){               /* 클라이언트와의 연결을 독립적으로 생성 */
			printf("fork error");
			close(clnt_sock);
			continue;
		}else if(pid > 0){          /* 부모 프로세스인 경우 */
 
			close(serv_sock);
			echo_serv(clnt_sock);
			printf("!!!연결 종료!!!\n");
			close(clnt_sock);
			return(0);
		}else{                      /* 자식 프로세스의 경우 */
			close(clnt_sock) ;
		}	
 
	}
	Commit_Oracle();
	close(clnt_sock);
 
	return(0);
}
 
int daemon_init()
{
	pid_t pid;
	if((pid = fork()) < 0)
   	return(-1);
   	else if(pid != 0)
   		exit(0); /* 부모프로세스는 종료시킨다 */		
	/* child continues */
   		setsid();        /* 스스로 세션의 리더가 된다 */
		umask(0);        /* clear our file mode creation mask */
		return(0);
}
 
void error_handling(char *message)
{
  fputs(message, stderr);
  fputc('\n', stderr);
  exit(1);
}
 
void z_handler(int sig)
{
  pid_t pid;
  int rtn;
  pid=waitpid(-1, &rtn, WNOHANG);
  printf("소멸된 좀비의 프로세스 ID : %d \n", pid);
  printf("리턴된 데이터 : %d \n\n", WEXITSTATUS(rtn));  
}
 
int Connect_Oracle(void)
{
 
	EXEC SQL BEGIN DECLARE SECTION;
		char uname[20];
		char passwd[20];	
	EXEC SQL END DECLARE SECTION;
		INITCHAR(uname);
		INITCHAR(passwd);
		strcpy(uname,"zipcode");
		strcpy(passwd,"zipcode");
	EXEC SQL CONNECT :uname IDENTIFIED BY :passwd;	
		if(sqlca.sqlcode != 0){
			printf(" DB CONNECT ERROR \n", sqlca.sqlcode);
			return(1);
		}else{
			printf(" DB CONNECT SUCCESS \n");
		}
		return(0);
}
 
int Commit_Oracle(void)
{
EXEC SQL COMMIT WORK RELEASE;
	printf("DB 접속 종료\n");
	return(0);
}
 
int echo_serv(int clnt_sock)
{
EXEC SQL BEGIN DECLARE SECTION;
	char ch[BUFSIZE];
	int str_len1;
	time_t s_time;
	char *id,*id2,*a,*b,*s,*s1;
EXEC SQL END DECLARE SECTION;
	struct eservstruct{
		char id[20];
		char id2[20];
		char pw[20];
		char message[BUFSIZE];
	};
	char buff[1000];
	struct eservstruct *i;		
	i = (struct eservstruct*) malloc( sizeof(struct eservstruct));
	memset(i, 0x00, sizeof(struct eservstruct));
	/* 자식 프로세스의 처리 영역: 데이터 수신 및 전송 */
	while(str_len1=read(clnt_sock,buff, sizeof(buff)) != 0){		
		s = strtok(buff,"|");
		s1 = strtok(NULL,"|");
		strcpy(i->id,s);
		strcpy(i->message,s1);
 
		time(&s_time);
		printf("접속중인 ID : [%s]\n", i->id);
		printf("메시지 수신시간 : %s", ctime(&s_time));
		/*printf("[%s]\n",message);*/
 
		printf("입력받은 메시지 : %s\n",i->message);
		printf("전달할 메시지 : %s\n\n",i->message);
 
		EXEC SQL INSERT INTO ECHO_SERV(I,T,A,B) 
		VALUES(:i->id, SYSDATE, :i->message, :i->message);
 
		EXEC SQL COMMIT;
 
		write(clnt_sock,i->message, str_len1); 
		memset(buff, 0x00, sizeof(buff));
	}
	free(i);		
}
 
 
(client)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <ctype.h> /* 문자 함수 */
 
#define BUFSIZE 1024
#define PORT 2100
void error_handling(char *message);
int join(int *new_num, char *id, char *pw);
 
int main(int argc, char **argv)
{
	int *num;
	char isalpha, isdigit;/* 영숫자 */
	int k=0;
	int a,n = 0;
	int i=0;
	char *id1;
	char *pw1;
	char new_check[10];
	int new_num;
	char *pw3;
	int pwcnt=0;
	char message[BUFSIZE];
  	int sock;
  	pid_t pid;
  	int str_len, recv_len, recv_num;
  	struct sockaddr_in serv_addr;
  	char buff[1000];
  	typedef struct{
	  	char id[20];
 	 	char pw[20];
 	 	char message[BUFSIZE];
 	 	char flag[100];
  	}clntstruct;  	
  	sock=socket(PF_INET, SOCK_STREAM, 0);
 
	clntstruct *j;
	j = malloc(sizeof(clntstruct));	   
 
  	memset(&serv_addr, 0, sizeof(serv_addr));
  	serv_addr.sin_family=AF_INET;
  	serv_addr.sin_addr.s_addr=inet_addr("127.0.0.1");
  	serv_addr.sin_port=htons(PORT);
 
  	if(connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr))==-1){
    	error_handling("connect() error!");
	}
 
	while(1){
		input :	printf("[1]회원가입 [2]로그인\n");
			scanf("%d",&k);
 
			if(k==1){/* 회원가입 */
				printf("New ID : ");
				scanf("%s",j->id);	
				printf("New PW : ");
				scanf("%s",j->pw);
 
				while(strlen(gets(j->pw))<10){               /* pw 10자리 미만 오류 */
					printf("PW ERROR\n");
					memset(j->pw, 0x00, sizeof(j->pw));
					printf("New PW : ");
				}
 
/*				if(isdigit(j->pw)) && (isalpha(j->pw)){                     /* 영,숫자만 한글 오류*/
/*					printf("PW ERROR\n");
					memset(j->pw, 0x00, sizeof(j->pw));
					return(0);
				} 		*/
/*			printf("pw : ");  */
				goto input;
			}
 
			else if(k==2){ /* 로그인 */
				printf("ID : ");
				scanf("%s",j->id);
				printf("PW : ");
				scanf("%s",j->pw);
 
				while(strlen(gets(j->id))>20){
					printf("ID ERROR\n");
					memset(j->id, 0x00, sizeof(j->id));
					printf("ID : ");
				}
					while(strlen(gets(j->pw))<10){              /* pw 10자리 미만 오류 */
						printf("PW ERROR\n");
					memset(j->pw, 0x00, sizeof(j->pw));
					printf("PW : ");
					}
 
					while(1){                                  /* 3회 오류 */
//						printf("PW ERROR\n");
						pwcnt++;
						memset(buff,0x00,sizeof(buff));
						if(pwcnt == 3){
							strcpy(j->flag,pw3);
							sprintf(buff,"%s|%s|%s",j->id,j->pw,j->flag);
							write(sock, buff, sizeof(buff));
							printf("PW 3 ERROR\n");
							return(0);
						}
//						memset(j->pw, 0x00, sizeof(j->pw));
//						printf("PW : ");
							sprintf(buff,"%s|%s|%s|",j->id,j->pw,j->flag);
							write(sock, buff, sizeof(buff));
							memset(buff,0x00,sizeof(buff));
							read(sock, buff, sizeof(buff));
							if(strcmp(buff,"p")){
								break;
							}
					}			
		/*			strcpy(id1,id);
					strcpy(pw1,pw);    */
					goto end;
			}
			end : printf("채팅접속!!\n");	
 
 
 
	while(1){
		fflush(stdin);
		printf("전송할 메시지를 입력하세요 (q,Q to quit) : ");
 
		if(strlen(gets(j->message))>BUFSIZE){
			printf("error");
			break;
		}
			if(!strcmp(j->message,"q")){
				break;
			}else if(!strcmp(j->message,"Q")){	
				break;
			}
			strcpy(buff,j->id);
			strcat(buff,"|");
			strcat(buff,j->message);
			strcat(buff,"|");		
			str_len=write(sock, buff, sizeof(buff));
			str_len = read(sock, j->message, sizeof(j->message));
			printf("서버로부터 전송된 메시지 : %s\n",j->message);
			memset(j->message,0x00,sizeof(j->message));
	}
	free(j);
	printf("CLIENT EXIT!!\n");
	close(sock);
	return(0);
	}
}
 
 
void error_handling(char *message)
{
	fputs(message, stderr);
  	fputc('\n', stderr);
  	exit(1);
}