客户端程序源代码

#include

#include

#include

#include

#include

#define rec_length 20

main(int argc, char **argv )

{

// structure defined for request as a client

struct hostent *hp1;

struct sockaddr_in sin1;

struct servent *sp1;

char sbuf[50];

int ss,spid;

char *sservice,*sdest;

// structure defined for request as a server

struct sockaddr_in sin;

struct servent *sp;

int s,ns,pid;

char buf[50];

char *service;

// test the environment parameter: lservice, dservice, server_name if(argc==4){ service=argv[1];sservice=argv[2]; sdest=argv[3];}

else {

fprintf(stderr,"Parameter assigned Error!\nUsage:\n");

fprintf(stderr,"\t%s lservice dservice server_name!\n",argv[0]);

fprintf(stderr,"Note: server_name is defined in file /etc/hosts\n");

fprintf(stderr,"and: lservice dservice are defined in file /etc/services\n");

exit(-1);

}

if((sp=getservbyname(service,"tcp"))==NULL){

fprintf(stderr,"Error: getservbyname");

exit(-5);

}

if((s=socket(AF_INET,SOCK_STREAM,0))==-1){

fprintf(stderr,"Error: socket create");

exit(-6);

}

bzero(&sin,sizeof(sin));

sin.sin_port=sp->s_port;

if(bind(s,&sin,sizeof(sin))==-1){

fprintf(stderr,"Error: bind");

close(s); exit(-6);

}

if(listen(s,5)==-1){

fprintf(stderr,"Error: listen");

close(s); exit(-6);

}

while(1){

fprintf(stderr,"\n\t\t\t Now wait connect ...\n");

if((ns=accept(s,0,0))==-1){ // wait a connection */

fprintf(stderr,"error: accept"); continue;

}

if((pid=fork())==-1){ // conneted, and then create child proc fprintf(stderr,"server: fork error!");

close(s); exit(-1);

}

if(pid!=0){ //parent proce, nothing to do, and to the next loop close(ns);wait(0);continue;

}

if(pid==0){ // entered child proccedure

close(s);

printf("Receive a client connect:%s\n",argv[1]);

if(read(ns,buf,rec_length)==0){

fprintf(stderr,"Read nothing from socket:ns\n");

close(ns); exit(-3);

}

printf("%s get message from ns: %s\n",argv[0],buf);

// request message got from the Client.

// Begine a Connection to Server as a Client

if((sp1=getservbyname(sservice,"tcp"))==NULL){

fprintf(stderr,"Error: getservbyname s1");

exit(-5);

}

if((hp1=gethostbyname(sdest))==0){

fprintf(stderr,"Error: gethostbyname s1");

exit(-6);

}

bzero(&sin1,sizeof(sin1));

bcopy(hp1->h_addr,&sin1.sin_addr,hp1->h_length);

sin1.sin_family=hp1->h_addrtype;

sin1.sin_port=sp1->s_port;

if((ss=socket(AF_INET,SOCK_STREAM,0))==-1){

fprintf(stderr,"Error: socket s1");

exit(-6);

}

if(connect(ss,&sin1,sizeof(sin1))==-1){

fprintf(stderr,"Error: connect s1");

close(ss); exit(-6);

}

// next 2 Line build request message

spid=getpid();

sprintf(sbuf,"%5.5d%5.5d%5.5d%5.5d",spid,spid*2,spid*3,spid*4);

fprintf(stderr,"%s is sending request message: %s s1\n",argv[0],sbuf);

if(write(ss,sbuf,rec_length)!=rec_length){ //to server

fprintf(stderr,"Write Socket ss ERROR! s1\n");

close(ss); exit(-1);

}

if(read(ss,sbuf,rec_length)==0){ //from server

fprintf(stderr,"Read Socket ss Error! s1\n");

close(ss); exit(-2);

}

printf("%s get reply: %s\n",argv[0],sbuf);

close(ss);

// End the Communication with my Server

// Next 2 Line, build a replay Message buf, and write it back

pid=getpid();

sprintf(buf,"%5.5d%5.5d%5.5d%5.5d",pid,pid*2,pid*3,pid*4);

fprintf(stderr," and, send it back to client: %s\n",buf);

if(write(ns,buf,rec_length)!=rec_length){

fprintf(stderr,"Write socket ns error!\n");

close(ns); exit(-4);

}

close(ns); exit(0);

}

}

}