linux c socket编程

这里主要是代码，网上有原理
socket 有同步，异步之分，我这是个同步的，同步又有阻塞和非阻塞之分，

这的非阻塞是用select()函数实现的
客户端：

#include <errno.h>
#include <sys/types.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <assert.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#define servport  2000 
#define maxdatasize 100

int main(int argc,char ** argv){

	int sockfd,recvbytes,f;
	char buf[maxdatasize];
	struct hostent *host;
	struct sockaddr_in serv_addr;
	 fd_set rfds,wfds;

	struct timeval timeout={10,0};
	
	if(argc<2){
		printf("please enter the service's hostname!\n");
		exit(1);
		
	}

	if((host=gethostbyname(argv[1]))==NULL){
	
		perror("gethostbyname error");
		exit(0);

	}
	if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1){ 
		
		perror("create socker error");
		exit(0);
	}	
	
	serv_addr.sin_family=AF_INET;
	serv_addr.sin_port=htons(servport);
	serv_addr.sin_addr=*((struct in_addr *)host->h_addr);
	bzero(&(serv_addr.sin_zero),8);
	if(connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(struct sockaddr))==-1){
		perror("connect error");
		exit(1);

	}

	while(1){
		tt:
	//	tt
		usleep(1000);
 		FD_ZERO(&rfds);
		FD_SET(sockfd,&rfds);
                FD_ZERO(&wfds);
		FD_SET(sockfd,&wfds);
		
		f=select(sockfd+1,&rfds,&wfds,NULL,&timeout);
		switch(f){
			case -1:
				perror("error");
				exit(0);
			case 0:
				perror("等待超时");
				goto tt ;
			default:
				if(FD_ISSET(sockfd,&rfds)){
				
					read(sockfd,&buf,50);
					printf("server data is :%s",&buf);
					
				}
				
				if(FD_ISSET(sockfd,&wfds)){
					write(sockfd,"$GPRMC,011728.000,A,3029.1966,N,11424.2966,E,8.34,280.72,110409,,,A*67",sizeof("$GPRMC,011728.000,A,3029.1966,N,11424.2966,E,8.34,280.72,110409,,,A*67"));
					printf("sent success");
				
				}
			
			

		}
	
/**
		if(f<=0){
		perror("select error");
		printf("connect error,sleep 1000");
		usleep(1000);
		continue ;

		}
		if(FD_ISSET(sockfd,&rfds)){
			
			read(sockfd,&buf,50);
			printf("read data is:%s",&buf);

		}
		if(FD_ISSET(sockfd,&wfds)){
			write(sockfd,"icome from client",50);
                        printf("client write something to server");
		

		}

**/
			
		
		

		
	/**

		if((recvbytes=read(sockfd,&buf,50))==-1){
		
			perror("read error");		
			exit(0);

		}
		buf[recvbytes]='\0';
		printf("read server  val:%s",buf);
		printf("enter content:");
	**/

//		int num=0;

//		while((content[num++]=getchar())!='\n');	

	
		
/**
	
		if(send(sockfd,&gd,sizeof(struct gpsdata),0)==-1){
			perror("write error");
			exit(0);

		}
**/
	//	write(sockfd,"\n",2);
	
	}
	
	return 0;

}//main

服务器端：

#include <stdio.h>
#include <stdlib.h>
#include <sys/select.h>
#include <errno.h>
#include <sys/types.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <assert.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
	#define SERVPORT 3333 
	#define BACKLOG  10
	#define dataSize 100
	main(){

		int sockfd,client_fd;		
		struct sockaddr_in my_addr;	
		struct sockaddr_in remote_addr;
		char buf[dataSize] ;
		fd_set rfds,wfds;
		
		struct timeval timeout={3,0};
		int tags;

		if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1){
		
			perror("socket create erro");
    			exit(1);
		}
		my_addr.sin_port=htons(SERVPORT);
		my_addr.sin_family=AF_INET;	
                my_addr.sin_addr.s_addr=INADDR_ANY;
                bzero(&(my_addr.sin_zero),8);

		if(bind(sockfd,(struct sockaddr *)&my_addr,sizeof(struct sockaddr))==-1){

			perror("bind error");
                        exit(1);
		}
		if(listen(sockfd,BACKLOG)==-1){
			perror("lister error");
			exit(1);
		}



		
		while(1) {
			int sin_size=sizeof(struct sockaddr_in);
			if((client_fd=accept(sockfd,(struct sockaddr *)&remote_addr,&sin_size))==-1){
			
				perror("accept error");
				continue;
			}
              
			printf("received a connection from %s\n",inet_ntoa(remote_addr.sin_addr));
		
       		       if(!fork()){
				char content[50];
			

                            while(1){
					gg: 
                                    
					FD_ZERO(&rfds);
					FD_SET(client_fd,&rfds);
					FD_ZERO(&wfds);
					FD_SET(client_fd,&wfds);
					tags=select(client_fd+1,&rfds,&wfds,NULL,&timeout);
					switch(tags){

						case -1:
							printf("出错");
							exit(-1); break;
						case 0:  
							printf("没有数据");
							continue gg ;
						default:
							if(FD_ISSET(client_fd,&rfds)){
								
								read(client_fd,&content,50);
                                                                printf("client data is :%s",&content);
							
							}
							if(FD_ISSET(client_fd,&wfds)){
                                                                write(client_fd,"i come from server ",50);
		
							}
							break;
					}
			    }

			
			close(client_fd);
			exit(0);
		     }
               }
	}