3 * Copyright (C) 2001-2003 Simone Piccardi
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or (at
8 * your option) any later version.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 /****************************************************************
22 * Elementary TCP server for echo service (port 7)
24 * Author: Simone Piccardi
27 * Usage: echod -h give all info
29 * $Id: TCP_echod_first.c,v 1.3 2003/12/25 17:31:09 piccardi Exp $
31 ****************************************************************/
33 * Include needed headers
35 #include <sys/types.h> /* predefined types */
36 #include <unistd.h> /* include unix standard library */
37 #include <arpa/inet.h> /* IP addresses conversion utiliites */
38 #include <sys/socket.h> /* socket library */
39 #include <stdio.h> /* include standard I/O library */
41 #include <syslog.h> /* syslog system functions */
42 #include <signal.h> /* signal functions */
43 #include <errno.h> /* error code */
44 #include <string.h> /* error strings */
51 int demonize = 1; /* daemon use option: default is daemon */
52 int debugging = 0; /* debug info printing option: default is no debug */
53 /* Subroutines declaration */
55 void ServEcho(int sockfd);
56 void PrintErr(char * error);
57 /* Program beginning */
58 int main(int argc, char *argv[])
61 * Variables definition
65 struct sockaddr_in serv_add;
67 * Input section: decode parameters passed in the calling
71 opterr = 0; /* don't want writing to stderr */
72 while ( (i = getopt(argc, argv, "hdi")) != -1) {
78 printf("Wrong -h option use\n");
88 case '?': /* unrecognized options */
89 printf("Unrecognized options -%c\n",optopt);
91 default: /* should not reached */
95 /* ***********************************************************
97 * Options processing completed
101 * ***********************************************************/
102 /* install SIGCHLD handler */
103 Signal(SIGCHLD, HandSigCHLD); /* establish handler */
105 if ( (list_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
106 perror("Socket creation error");
109 /* initialize address */
110 memset((void *)&serv_add, 0, sizeof(serv_add)); /* clear server address */
111 serv_add.sin_family = AF_INET; /* address type is INET */
112 serv_add.sin_port = htons(7); /* echo port is 7 */
113 serv_add.sin_addr.s_addr = htonl(INADDR_ANY); /* connect from anywhere */
115 if (bind(list_fd, (struct sockaddr *)&serv_add, sizeof(serv_add)) < 0) {
116 perror("bind error");
119 /* release privileges and go daemon */
120 if (setgid(65534) !=0) { /* first give away group privileges */
121 perror("cannot give away group privileges");
124 if (setuid(65534) !=0) { /* and only after user ... */
125 perror("cannot give away user privileges");
128 if (demonize) { /* go daemon */
129 openlog(argv[0], 0, LOG_DAEMON); /* open logging */
130 if (daemon(0, 0) != 0) {
131 perror("cannot start as daemon");
136 if (listen(list_fd, BACKLOG) < 0 ) {
137 PrintErr("listen error");
140 /* handle echo to client */
142 /* accept connection */
143 len = sizeof(cli_add);
144 if ( (conn_fd = accept(list_fd, NULL, NULL)) < 0) {
145 PrintErr("accept error");
148 /* fork to handle connection */
149 if ( (pid = fork()) < 0 ){
150 PrintErr("fork error");
153 if (pid == 0) { /* child */
154 close(list_fd); /* close listening socket */
155 ServEcho(conn_fd); /* handle echo */
157 } else { /* parent */
158 close(conn_fd); /* close connected socket */
161 /* normal exit, never reached */
165 * routine to print usage info and exit
168 printf("Elementary echo server\n");
170 printf(" echod [-h] \n");
171 printf(" -h print this help\n");
172 printf(" -d print debug info\n");
173 printf(" -i use interactively\n");
177 * routine to handle echo for connection
179 void ServEcho(int sockfd) {
180 char buffer[MAXLINE];
182 char debug[MAXLINE+20];
184 /* main loop, reading 0 char means client close connection */
185 while ( (nread = read(sockfd, buffer, MAXLINE)) != 0) {
186 nwrite = FullWrite(sockfd, buffer, nread);
188 PrintErr("write error");
194 * routine to print error on stout or syslog
196 void PrintErr(char * error) {
197 if (demonize) { /* daemon mode */
198 syslog(LOG_ERR, "%s: %m", error); /* log string and error message */