ドツボにはまったのでメモ

ソケット通信のプログラムを書くときにwrite関数を使用する場合，サイズ指定はstrlen関数を使用すること．read関数と同じようにsizeofを使ってしまい，原因不明のバグに半日悩まされたのでメモしておきます．
あとサンプルも書いておこうかな．
C言語でlinux(Vine)でローカルのSMTPサーバに接続しローカルユーザーにメールを送信するサンプルです．多少の不備はご愛嬌で．参考にしたのはhttp://www.site-cooler.com/kwl/perl/smtp.htmで先にperlでサンプルを動かしてから作りました．

#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define BUF_SIZE 1024

int main(void){
	char server = "localhost";
	char to = "user@localhost";
	char from = "c_program@localhost";
	char subject = "test";
	char data[] = "hogehoge";

	char send_data[BUF_SIZE];
	char write_buf[BUF_SIZE];
	char read_buf[BUF_SIZE];
	char* ptr;

	int sock;
	int len;
	struct sockaddr_in addr;
	int result;
	int i;
	
	memset(send_data,0,sizeof(send_data));
	sprintf(send_data,"X-Mailer:SMTP Sample\nContent-Type:text/plain;charset=iso-2022-jp\nFrom:%s<%s>\nTo

%s\nSubject
%s\n\n%s\n.\n",from,from,to,subject,data);
#if 0
	printf("[%s]\n\n",send_data);
#endif

	
	sock = socket(AF_INET,SOCK_STREAM,0);
	if(sock == -1){
		perror("socket:");
		exit(1);
	}
	addr.sin_family	= AF_INET;
	addr.sin_addr.s_addr = inet_addr("127.0.0.1");
	addr.sin_port= htons(25);
	len = sizeof(addr);

	result = connect(sock,(struct sockaddr*)&addr,len);
	if(result == -1){
		perror("connect:");
		exit(1);
	}
	memset(read_buf,0,sizeof(read_buf));
	memset(write_buf,0,sizeof(write_buf));
	read(sock,read_buf,sizeof(read_buf));
#if 0
	printf("<-%s",read_buf);
#endif
	ptr = &read_buf[0];
	result = 0;
	len = sizeof(read_buf);
	do{
		if(strncmp(ptr,"220",3) == 0 ){
			result = 1; break;
		}
		ptr++;
	}while(result == 1);
	if(result != 1){
		printf("Connect error\n");
		close(sock);
		exit(1);
	}

	memset(read_buf,0,sizeof(read_buf));
	memset(write_buf,0,sizeof(write_buf));
	sprintf(write_buf,"HELO %s\r\n",server);
	write(sock,write_buf,strlen(write_buf));
	read(sock,read_buf,sizeof(read_buf));
#if 0
	printf("->%s",write_buf);
	printf("<-%s",read_buf);
#endif
	ptr = &read_buf[0];
	result = 0;
	do{
		if(strncmp(ptr,"250",3) == 0){
			result = 1; break;
		}
		ptr++;
	}while(result == 1);
	if(result != 1){
		printf("HELO error\n");
		close(sock);
		exit(1);
	}
	
	memset(read_buf,0,sizeof(read_buf));
	memset(write_buf,0,sizeof(write_buf));
	sprintf(write_buf,"Mail From:<%s>\r\n",from);
	write(sock,write_buf,strlen(write_buf));
	read(sock,read_buf,sizeof(read_buf));
#if 0
	printf("->%s",write_buf);
	printf("<-%s",read_buf);
#endif
	ptr = &read_buf[0];
	result = 0;
	do{
		if(strncmp(ptr,"250",3) == 0){
			result = 1; break;
		}
		ptr++;
	}while(result == 1);
	if(result != 1){
		printf("Mail From error\n");
		close(sock);
		exit(1);
	}
	
	memset(read_buf,0,sizeof(read_buf));
	memset(write_buf,0,sizeof(write_buf));
	sprintf(write_buf,"RCPT To:<%s>\r\n",to);
	write(sock,write_buf,strlen(write_buf));
	read(sock,read_buf,sizeof(read_buf));
#if 0
	printf("->%s",write_buf);
	printf("<-%s",read_buf);
#endif
	ptr = &read_buf[0];
	result = 0;
	do{
		if(strncmp(ptr,"250",3) == 0 || strncmp(ptr,"251",3) == 0){
			result = 1;
			break;
		}
		ptr++;
	}while(result == 1);
	if(result != 1){
		printf("RCPT error\n");
		close(sock);
		exit(1);
	}
	
	memset(read_buf,0,sizeof(read_buf));
	memset(write_buf,0,sizeof(write_buf));
	sprintf(write_buf,"DATA\r\n");
	write(sock,write_buf,strlen(write_buf));
	read(sock,read_buf,sizeof(read_buf));
#if 0
	printf("->%s",write_buf);
	printf("<-%s",read_buf);
#endif
	ptr = &read_buf[0];
	result = 0;
	do{
		if(strncmp(ptr,"354",3) == 0){
			result = 1; break;
		}
		ptr++;
	}while(result == 1);
	if(result != 1){
		printf("DATA error\n");
		close(sock);
		exit(1);
	}
	
	memset(read_buf,0,sizeof(read_buf));
	memset(write_buf,0,sizeof(write_buf));
	sprintf(write_buf,"%s",send_data);
	write(sock,write_buf,strlen(write_buf));
	read(sock,read_buf,sizeof(read_buf));
#if 0
	printf("->%s",write_buf);
	printf("<-%s",read_buf);
#endif
	ptr = &read_buf[0];
	result = 0;
	do{
		if(strncmp(ptr,"250",3) == 0){
			result = 1; break;
		}
		ptr++;
	}while(result == 1);
	if(result != 1){
		printf("Send error\n");
		close(sock);
		exit(1);
	}
	
	sprintf(write_buf,"QUIT\r\n");
	write(sock,write_buf,strlen(write_buf));

	printf("program end\n");
	return 0;
}

そうだ．あとこのプログラム中の宛先ポート指定でhtonsを忘れてこれもはまった．