LInux下网络通信编程实例

服务器端和客户端使用TCP的流程图：

服务器端：socket->bind->listen->accept->recv/recvfrom->send/sendto->close

客户端：socket->connect->send/sendto->recv/recvfrom->close

其中服务器端首先建立起socket，然后调用本地端口的绑定，接着就开始与客服端建立联系，并接收客户端发送的消息。客户端则在建立socket之后调用connect函数来建立连接。

服务器端的源代码如下所示：

/*"server.c"*/

#include<sys/types.h>

#include<sys/socket.h>

#include<stdio.h>

#include<stdlib.h>

#include<errno.h>

#include<string.h>

#include<unistd.h>

#include<netinet/in.h>

#define PORT 4321

#define BUFFER_SIZE 1024

#define MAX_QUE_CONN_NM 5

int main(){

struct sockaddr_in server_sockaddr,client_sockaddr;

int sin_size,recvbytes;

int sockfd,client_fd;

char buf[BUFFER_SIZE];

if((sockfd = socket(AF_INET,SOCK_STREAM,0))== -1){ //建立socket连接

perror("socket");

exit(1);

}

printf("Socket id=%d/n",sockfd);

/*设置sockaddr_in结构体中的相关参数*/

server_sockaddr.sin_family = AF_INET;

server_sockaddr.sin_port = htons(PORT);

server_sockaddr.sin_addr.s_addr = INADDR_ANY;

bzero(&(server_sockaddr.sin_zero),8);

int i = 1; //允许重复使用本地地址与套接字进行绑定

setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&i,sizeof(i));

if(bind(sockfd,(struct sockaddr *)&server_sockaddr,sizeof(struct sockaddr)) == -1){ //绑定函数bind

perror("bind");

exit(1);

}

printf("Bind success!/n");

if(listen(sockfd,MAX_QUE_CONN_NM)== -1){ //调用listen函数，创建为处理请求的队列

perror("listen");

exit(1);

}

printf("Listening....../n");

if((client_fd = accept(sockfd,(struct sockaddr *)&client_sockaddr,&sin_size))==-1){//调用accept函数，等待客户端的接

perror("accept");

exit(1);

}

memset(buf,0,sizeof(buf));

if((recvbytes = recv(client_fd,buf,BUFFER_SIZE,0)) == -1){//调用recv函数接收客户端的请求

perror("recv");

exit(1);

}

printf("Received a message: %s/n",buf);

close(sockfd);

exit(0);

}

客户端的源代码如下所示：

/*"client.c"*/

#include<sys/types.h>

#include<sys/socket.h>

#include<stdio.h>

#include<stdlib.h>

#include<errno.h>

#include<string.h>

#include<unistd.h>

#include<netinet/in.h>

#define PORT 4321

#define BUFFER_SIZE 1024

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

int socdfd,sendbytes;

char buf[BUFFER_SIZE];

struct hostent *host;

struct sockaddr_in serv_addr;

if(argc < 3){

fprintf(stderr,"USAGE:./client Hostname(or ip address) Text/n");

exit(1);

}

if((host = gethostbyname(argv[1])) == NULL){//地址解析函数

perror("gethostbyname");

exit(1);

}

memset(buf,0,sizeof(buf));

sprintf("buf,%"s",argv[2]");

if((sockfd = socket(AF_INET, SOCK_STREAM,0)) == -1){ //创建socket

perror("socket");

exit(1);

}

server_addr.sin_family = AF_INET; //设置sockaddr_in结构体中相关参数

server_addr.sin_port = htons(PORT);

server_addr.sin_addr= *((struct in_addr *)host->h_addr);

bzero(&(server_sockaddr.sin_zero),8);

if(connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(struct sockadddr))== -1){ //调用connect函数主动发起对服务器端的连接

perror("connect");

exit(1);

}

if((sendbytes = send(sockfd,buf,strlen(buf),0)) == -1){//发送消息给服务器端

perror("send");

exit(1);

}

close(sockfd);

exit(0);

}