diff --git a/client.c b/client.c
index 1581068..964804c 100644
--- a/client.c
+++ b/client.c
@@ -9,188 +9,156 @@
 #include <arpa/inet.h>
 #include <errno.h>
 #include <sys/stat.h>
-#include <signal.h>
+
 #include <assert.h>
 #include <fcntl.h>
 #include "socket_wrapper.h"
 
+#ifdef USE_SENDFILE
+#include <sys/sendfile.h>
+const size_t SEND_FILE_CHUNK_SIZE = 0x100000; /*1MB*/
+#endif
+
 /*========
  *Operation
  *========*/
-/*send user error message
-80 character limit
-*/
-int send_fail(int sock,const char * msg){
-    struct TransferResult res;
-    res.res = RES_USR_ERR;
-    res.file_size = 0;
-    res.err_number = 0;
-    res.error_msg_size = strlen(msg);
-    //os will be combining if tcp_autocorking emabled.
-    if(send(sock,&res,sizeof(res),0) < 0){
-        perror("error msg send");
+
+int sendReadOp(int sock,const char * filename){
+    struct ReadOp op;
+    op.file_url_size = strlen(filename);
+    op.padding0 = 0;
+    if(send(sock,&op,sizeof(op),0)<0){
+        perror("readop send fail");
         return -1;
     }
-    if (send(sock,msg,res.error_msg_size,0) < 0){
-        perror("error msg send");
+    if(send(sock,filename,op.file_url_size,0)<0){
+        perror("readop filename send fail");
         return -1;
     }
     return 0;
 }
 
-int send_errno(int sock){
-    struct TransferResult r;
-    r.res = RES_ERR;
-    r.err_number = errno;
-    r.file_size = 0;
-    r.error_msg_size = 0;
-    if(send(sock,&r,sizeof(r),0)){
-        perror("errno send");
-        return -1;
-    }
-    return 0;
-}
-/* return fd, if success.
-otherwise, return -1.
-*/
-int read_request(int sock,uint8_t * buf,size_t bufsize){
-    struct ReadOp p;
+int recvFile(int sock, const char * filename,size_t file_size){
     int fd;
-    ssize_t n = recv_until_byte(sock,&p,sizeof(p),TIMEOUT);
-    if (n < 0){
-        if (n == -2) fprintf(stderr,"timeout!");
-        else perror("receive fail"); 
+    size_t count = 0;
+    int i;
+    int cur_progress = 1;
+    int return_value = 0;
+    int buf_sz = getBufferSizeFrom(sock);
+    uint8_t * buf = malloc(buf_sz*sizeof(*buf));
+    if (buf == NULL){
         return -1;
     }
-    if(bufsize <= p.file_url_size + sizeof(p) + 1){
-        send_fail(sock,"buffer overflow");
-        return -1;
-    }
-    else if(p.file_url_size + 1 > MAX_PATH_SIZE){
-        send_fail(sock,"max path fail");
-        return -1;
-    }
-    else if(p.file_url_size == 0){
-        send_fail(sock,"filename zero fail");
-        return -1;
-    }
-    n = recv_until_byte(sock,buf,p.file_url_size,TIMEOUT);
-    buf[p.file_url_size] = '\0';
-    printf("str size: %d, request %s\n",p.file_url_size,buf);
-    if(strchr((char *)buf,'/') != NULL){
-        send_fail(sock,"Illegal character /");
-        return -1;
-    }
-    fd = open((char *)buf,O_RDONLY);
-    if(fd < 0){
-        send_errno(sock);
-        close(fd);
-        return -1;
-    }
-    return fd;
-}
-
-int send_response(int sock,int fd, uint8_t * buf, size_t bufsize){
-    struct TransferResult r;
-    struct stat st;
-    off_t offset = 0;
-    ssize_t readed = 0;
-    r.res = RES_OK;
-    r.err_number = 0;
-    r.error_msg_size = 0;
-    if(fstat(fd,&st) < 0){
-        return send_errno(sock);
-    }
-    if(S_ISDIR(st.st_mode)){
-        return send_fail(sock,"is a directory");
-    }
-    r.file_size = st.st_size;
-    if(send(sock,&r,sizeof(r),0)<0){
-        perror("send fail");
-        return -1;
-    }
-#ifdef USE_SENDFILE
-    while (r.file_size != offset)
+    fd = open(filename,O_WRONLY|O_CREAT|O_TRUNC,S_IRWXU|S_IRWXG|S_IROTH);
+    if (fd < 0)
     {
-        size_t count = SEND_FILE_CHUNK_SIZE < (r.file_size - offset) ? SEND_FILE_CHUNK_SIZE : (r.file_size - offset);
-        if((readed = sendfile(sock,fd,&offset,count)) < 0){
-            perror("send file fail");
-            return -1;
-        }
-    }
-#else
-    while (offset < r.file_size)
-    {
-        readed = bufsize < (r.file_size - offset) ? bufsize : r.file_size - offset;
-        if(read(fd,buf,readed)<0){
-            perror("send response read fail");
-            return -1;
-        }
-        if(send(sock,buf,readed,0)<0){
-            perror("send response send fail");
-            return -1;
-        }
-        offset += readed;
+        perror("file open fail");
+        return -1;
     }
     
-#endif
+    while (file_size - count > 0)
+    {
+        int readed = buf_sz < file_size - count ? buf_sz : file_size - count;
+        if((i = recv_until_byte(sock,buf,readed,TIMEOUT)) < 0){
+            if(i == -2) 
+                fprintf(stderr,"recv file failed : timeout connetion lost\n");
+            else perror("recv file failed");
+            return_value = -1;
+            goto END;
+        }
+        if(write(fd,buf,readed)<0){
+            perror("file write failed");
+            return_value = -1;
+            goto END;
+        }
+        if( ((double)count / (double)file_size) * 100.0 > ((double)cur_progress) ){
+            printf("\rprogress : %d%% current bytes: %ld bytes",cur_progress,count);
+            cur_progress = (int)((((double)count / (double)file_size)) * 100.0 + 1.0);
+            fflush(stdout);
+        }
+        count += readed;
+    }
+    printf("\rprogress : 100.00%% current bytes: %ld bytes\n",count);
+END:
+    free(buf);
+    return return_value;
+}
+
+int recvData(int sock,const char * filename){
+    struct TransferResult res;
+    int i=0;
+    if((i=recv_until_byte(sock,&res,sizeof(res),TIMEOUT)) < 0){
+        if (i == -2) fprintf(stderr,"timeout");
+        else perror("recv fail");
+        return -1;
+    }
+    static char error_meesage_buf[80] = "";
+    switch(res.res){
+        case RES_ERR:
+            fprintf(stderr,"Server Fail: %s", strerror(res.err_number));
+            return -1;
+        case RES_USR_ERR:
+            assert(res.error_msg_size < 80);/*todo : fix*/
+            if((i=recv_until_byte(sock,error_meesage_buf,res.error_msg_size,TIMEOUT)) < 0){
+                if (i == -2) fprintf(stderr,"timeout");
+                else perror("recv fail");
+                return -1;
+            }
+            fprintf(stderr,"Error Message From Server: %s",error_meesage_buf);
+            return -1;
+        case RES_OK:
+            return recvFile(sock,filename,res.file_size);
+            break;
+        default:
+            fprintf(stderr,"unknown value!");
+            return -1;
+    }
+
     return 0;
 }
-static int sock;
-void safe_exit(){
-    close(sock);
-}
+
 int main(int argc, const char *argv[]){
-    uint8_t * buf;
     struct sockaddr_in addr;
-    struct sockaddr_in client_addr;
-    socklen_t client_addr_len = sizeof(client_addr);
-    int csock;
-    int bufsize;
+    const char * filename;
+    const char * server_name;
+    in_port_t server_port = SERVER_PORT;
+    int sock;
     register_alarm();
+    if (argc != 4){
+        fprintf(stderr,"invaild arguments number.");
+        return 1;
+    }
+    server_name = argv[1];
+    server_port = atoi(argv[2]);
+    filename = argv[3];
+    if (server_port == 0)
+    {
+        fprintf(stderr,"port invalid");
+        return 1;
+    }
     sock = socket(AF_INET,SOCK_STREAM,0);
-    atexit(safe_exit);
     if(sock < 0){
         perror("sock create fail");
         return 1;
     }
-    bufsize = getBufferSizeFrom(sock);
-    buf = malloc(bufsize * sizeof(*buf));
-    if (buf == NULL){
-        fprintf(stderr,"lack of memory");
-        return 1;
-    }
-    
-    addr.sin_addr.s_addr = htonl(INADDR_ANY); /*0.0.0.0 모든 네트워크 인터페이스에 묶임.*/
-    addr.sin_family = AF_INET;
-    addr.sin_port = htons(SERVER_PORT);
-
-    if(bind(sock, (struct sockaddr *)&addr,sizeof(addr)) < 0){
-        perror("bind failed");
-        return 1;
-    }
-    fprintf(stderr,"server bind on %s:%d\n",inet_ntoa(addr.sin_addr),SERVER_PORT);
-
-    if(listen(sock,1) < 0){
-        perror("listen failed");
-        return 1;
-    }
-
-    while ((csock = accept(sock, (struct sockaddr *)&client_addr,&client_addr_len)) >= 0)
     {
-        int fd;
-        /*inet_ntoa is not reentrant function. do not use it in signal handler.*/
-        printf("Connect : %s\n",(inet_ntoa(client_addr.sin_addr)));
-        if((fd = read_request(csock,buf,bufsize)) > 0){
-            send_response(csock,fd,buf,bufsize);
-            close(fd);
+        int option = 1;
+        if(setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,&option,sizeof(option)) < 0){
+            perror("setsockopt");
         }
-
-        if(close(csock) < 0)
-            perror("csock close error");
-
     }
-    free(buf);
-    perror("accept error");
-    return 1;
+    addr.sin_addr.s_addr = inet_addr(server_name);
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(server_port);
+    if(connect(sock,(struct sockaddr *)&addr,sizeof(addr)) < 0){
+        perror("connect failed");
+        return 1;
+    }
+    if(sendReadOp(sock,filename) == 0){
+        int ret = recvData(sock,filename);
+        close(sock);
+        return ret;
+    }
+    close(sock);
+    return 0;
 }
\ No newline at end of file
diff --git a/server.c b/server.c
index 964804c..1581068 100644
--- a/server.c
+++ b/server.c
@@ -9,156 +9,188 @@
 #include <arpa/inet.h>
 #include <errno.h>
 #include <sys/stat.h>
-
+#include <signal.h>
 #include <assert.h>
 #include <fcntl.h>
 #include "socket_wrapper.h"
 
-#ifdef USE_SENDFILE
-#include <sys/sendfile.h>
-const size_t SEND_FILE_CHUNK_SIZE = 0x100000; /*1MB*/
-#endif
-
 /*========
  *Operation
  *========*/
-
-int sendReadOp(int sock,const char * filename){
-    struct ReadOp op;
-    op.file_url_size = strlen(filename);
-    op.padding0 = 0;
-    if(send(sock,&op,sizeof(op),0)<0){
-        perror("readop send fail");
+/*send user error message
+80 character limit
+*/
+int send_fail(int sock,const char * msg){
+    struct TransferResult res;
+    res.res = RES_USR_ERR;
+    res.file_size = 0;
+    res.err_number = 0;
+    res.error_msg_size = strlen(msg);
+    //os will be combining if tcp_autocorking emabled.
+    if(send(sock,&res,sizeof(res),0) < 0){
+        perror("error msg send");
         return -1;
     }
-    if(send(sock,filename,op.file_url_size,0)<0){
-        perror("readop filename send fail");
+    if (send(sock,msg,res.error_msg_size,0) < 0){
+        perror("error msg send");
         return -1;
     }
     return 0;
 }
 
-int recvFile(int sock, const char * filename,size_t file_size){
-    int fd;
-    size_t count = 0;
-    int i;
-    int cur_progress = 1;
-    int return_value = 0;
-    int buf_sz = getBufferSizeFrom(sock);
-    uint8_t * buf = malloc(buf_sz*sizeof(*buf));
-    if (buf == NULL){
+int send_errno(int sock){
+    struct TransferResult r;
+    r.res = RES_ERR;
+    r.err_number = errno;
+    r.file_size = 0;
+    r.error_msg_size = 0;
+    if(send(sock,&r,sizeof(r),0)){
+        perror("errno send");
         return -1;
     }
-    fd = open(filename,O_WRONLY|O_CREAT|O_TRUNC,S_IRWXU|S_IRWXG|S_IROTH);
-    if (fd < 0)
-    {
-        perror("file open fail");
+    return 0;
+}
+/* return fd, if success.
+otherwise, return -1.
+*/
+int read_request(int sock,uint8_t * buf,size_t bufsize){
+    struct ReadOp p;
+    int fd;
+    ssize_t n = recv_until_byte(sock,&p,sizeof(p),TIMEOUT);
+    if (n < 0){
+        if (n == -2) fprintf(stderr,"timeout!");
+        else perror("receive fail"); 
         return -1;
     }
+    if(bufsize <= p.file_url_size + sizeof(p) + 1){
+        send_fail(sock,"buffer overflow");
+        return -1;
+    }
+    else if(p.file_url_size + 1 > MAX_PATH_SIZE){
+        send_fail(sock,"max path fail");
+        return -1;
+    }
+    else if(p.file_url_size == 0){
+        send_fail(sock,"filename zero fail");
+        return -1;
+    }
+    n = recv_until_byte(sock,buf,p.file_url_size,TIMEOUT);
+    buf[p.file_url_size] = '\0';
+    printf("str size: %d, request %s\n",p.file_url_size,buf);
+    if(strchr((char *)buf,'/') != NULL){
+        send_fail(sock,"Illegal character /");
+        return -1;
+    }
+    fd = open((char *)buf,O_RDONLY);
+    if(fd < 0){
+        send_errno(sock);
+        close(fd);
+        return -1;
+    }
+    return fd;
+}
+
+int send_response(int sock,int fd, uint8_t * buf, size_t bufsize){
+    struct TransferResult r;
+    struct stat st;
+    off_t offset = 0;
+    ssize_t readed = 0;
+    r.res = RES_OK;
+    r.err_number = 0;
+    r.error_msg_size = 0;
+    if(fstat(fd,&st) < 0){
+        return send_errno(sock);
+    }
+    if(S_ISDIR(st.st_mode)){
+        return send_fail(sock,"is a directory");
+    }
+    r.file_size = st.st_size;
+    if(send(sock,&r,sizeof(r),0)<0){
+        perror("send fail");
+        return -1;
+    }
+#ifdef USE_SENDFILE
+    while (r.file_size != offset)
+    {
+        size_t count = SEND_FILE_CHUNK_SIZE < (r.file_size - offset) ? SEND_FILE_CHUNK_SIZE : (r.file_size - offset);
+        if((readed = sendfile(sock,fd,&offset,count)) < 0){
+            perror("send file fail");
+            return -1;
+        }
+    }
+#else
+    while (offset < r.file_size)
+    {
+        readed = bufsize < (r.file_size - offset) ? bufsize : r.file_size - offset;
+        if(read(fd,buf,readed)<0){
+            perror("send response read fail");
+            return -1;
+        }
+        if(send(sock,buf,readed,0)<0){
+            perror("send response send fail");
+            return -1;
+        }
+        offset += readed;
+    }
     
-    while (file_size - count > 0)
-    {
-        int readed = buf_sz < file_size - count ? buf_sz : file_size - count;
-        if((i = recv_until_byte(sock,buf,readed,TIMEOUT)) < 0){
-            if(i == -2) 
-                fprintf(stderr,"recv file failed : timeout connetion lost\n");
-            else perror("recv file failed");
-            return_value = -1;
-            goto END;
-        }
-        if(write(fd,buf,readed)<0){
-            perror("file write failed");
-            return_value = -1;
-            goto END;
-        }
-        if( ((double)count / (double)file_size) * 100.0 > ((double)cur_progress) ){
-            printf("\rprogress : %d%% current bytes: %ld bytes",cur_progress,count);
-            cur_progress = (int)((((double)count / (double)file_size)) * 100.0 + 1.0);
-            fflush(stdout);
-        }
-        count += readed;
-    }
-    printf("\rprogress : 100.00%% current bytes: %ld bytes\n",count);
-END:
-    free(buf);
-    return return_value;
-}
-
-int recvData(int sock,const char * filename){
-    struct TransferResult res;
-    int i=0;
-    if((i=recv_until_byte(sock,&res,sizeof(res),TIMEOUT)) < 0){
-        if (i == -2) fprintf(stderr,"timeout");
-        else perror("recv fail");
-        return -1;
-    }
-    static char error_meesage_buf[80] = "";
-    switch(res.res){
-        case RES_ERR:
-            fprintf(stderr,"Server Fail: %s", strerror(res.err_number));
-            return -1;
-        case RES_USR_ERR:
-            assert(res.error_msg_size < 80);/*todo : fix*/
-            if((i=recv_until_byte(sock,error_meesage_buf,res.error_msg_size,TIMEOUT)) < 0){
-                if (i == -2) fprintf(stderr,"timeout");
-                else perror("recv fail");
-                return -1;
-            }
-            fprintf(stderr,"Error Message From Server: %s",error_meesage_buf);
-            return -1;
-        case RES_OK:
-            return recvFile(sock,filename,res.file_size);
-            break;
-        default:
-            fprintf(stderr,"unknown value!");
-            return -1;
-    }
-
+#endif
     return 0;
 }
-
+static int sock;
+void safe_exit(){
+    close(sock);
+}
 int main(int argc, const char *argv[]){
+    uint8_t * buf;
     struct sockaddr_in addr;
-    const char * filename;
-    const char * server_name;
-    in_port_t server_port = SERVER_PORT;
-    int sock;
+    struct sockaddr_in client_addr;
+    socklen_t client_addr_len = sizeof(client_addr);
+    int csock;
+    int bufsize;
     register_alarm();
-    if (argc != 4){
-        fprintf(stderr,"invaild arguments number.");
-        return 1;
-    }
-    server_name = argv[1];
-    server_port = atoi(argv[2]);
-    filename = argv[3];
-    if (server_port == 0)
-    {
-        fprintf(stderr,"port invalid");
-        return 1;
-    }
     sock = socket(AF_INET,SOCK_STREAM,0);
+    atexit(safe_exit);
     if(sock < 0){
         perror("sock create fail");
         return 1;
     }
-    {
-        int option = 1;
-        if(setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,&option,sizeof(option)) < 0){
-            perror("setsockopt");
-        }
-    }
-    addr.sin_addr.s_addr = inet_addr(server_name);
-    addr.sin_family = AF_INET;
-    addr.sin_port = htons(server_port);
-    if(connect(sock,(struct sockaddr *)&addr,sizeof(addr)) < 0){
-        perror("connect failed");
+    bufsize = getBufferSizeFrom(sock);
+    buf = malloc(bufsize * sizeof(*buf));
+    if (buf == NULL){
+        fprintf(stderr,"lack of memory");
         return 1;
     }
-    if(sendReadOp(sock,filename) == 0){
-        int ret = recvData(sock,filename);
-        close(sock);
-        return ret;
+    
+    addr.sin_addr.s_addr = htonl(INADDR_ANY); /*0.0.0.0 모든 네트워크 인터페이스에 묶임.*/
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(SERVER_PORT);
+
+    if(bind(sock, (struct sockaddr *)&addr,sizeof(addr)) < 0){
+        perror("bind failed");
+        return 1;
     }
-    close(sock);
-    return 0;
+    fprintf(stderr,"server bind on %s:%d\n",inet_ntoa(addr.sin_addr),SERVER_PORT);
+
+    if(listen(sock,1) < 0){
+        perror("listen failed");
+        return 1;
+    }
+
+    while ((csock = accept(sock, (struct sockaddr *)&client_addr,&client_addr_len)) >= 0)
+    {
+        int fd;
+        /*inet_ntoa is not reentrant function. do not use it in signal handler.*/
+        printf("Connect : %s\n",(inet_ntoa(client_addr.sin_addr)));
+        if((fd = read_request(csock,buf,bufsize)) > 0){
+            send_response(csock,fd,buf,bufsize);
+            close(fd);
+        }
+
+        if(close(csock) < 0)
+            perror("csock close error");
+
+    }
+    free(buf);
+    perror("accept error");
+    return 1;
 }
\ No newline at end of file