TCP
Server:
#include <stdlib.h>#include <stdio.h>#include <errno.h>#include <string.h>#include <netdb.h>#include <sys/types.h>#include <netinet/in.h>#include <sys/socket.h>#include <arpa/inet.h>int main(int argc, char** argv){int sockfd, new_fd;struct sockaddr_in server_addr; //服务器地址struct sockaddr_in client_addr; //客户端地址int sin_size, portnumber;const char hello[]="Hello\n";if(argc!=2){fprintf(stderr,"Usage:%s portnumber\a\n",argv[0]); exit(1);}if((portnumber=atoi(argv[1]))<0){fprintf(stderr,"Usage:%s portnumber\a\n",argv[0]);exit(1);}if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){ //建立套接字，范围值为整数描述符fprintf(stderr,"Socket error:%s \n\a",strerror(errno));exit(1);}//服务器填充sockaddr结构bzero(&server_addr,sizeof(struct sockaddr_in));server_addr.sin_family = AF_INET; //判断sockaddr_in 存储的是什么类型数据，不会发送到网络，所以无需字节顺序转换//注释：节顺序转换： htonl：Host to Network Long htons:Host to Network Shortserver_addr.sin_addr.s_addr = htonl(INADDR_ANY);//INADDR_ANY：任意IP地址 表示服务器接收任意外部连接 //server_addr.sin_addr.s_addr = inet_addr("192.168.1.103");server_addr.sin_port = htons(portnumber);//绑定的端口号portnumber 0~65535 //说明：1）端口号为0表示由系统分配可用端口 2）小于1024的端口需要root权限 3）如果设置的端口号已分配给其他进程，bind出错if(bind(sockfd,(struct sockaddr*)(&server_addr),sizeof(struct sockaddr))== -1){ //捆绑sockfd描述符到本地端口和地址fprintf(stderr,"Bind error%s\n\a",strerror(errno));exit(1);}if(listen(sockfd,5)== -1){//本地等待最大连接数5： 5~10fprintf(stderr,"Listen error %s\n\a",strerror(errno));exit(1);}while(1){sin_size = sizeof(struct sockaddr_in);if((new_fd = accept(sockfd ,(struct sockaddr *)(&client_addr),&sin_size))==-1){ //阻塞直到有连接请求，将远程计算机地址信息写入client_addr //new_fd 新socket sockfd用于倾听客户端请求，new_fd用于和已连接客户端通信fprintf(stderr,"Accept error %s\n\a",strerror(errno));exit(1);}//inet_ntoa: 把网络字节顺序的in_addr结构转换成 点分十进制字符串（如192.168.1.1）fprintf(stderr,"Server get connection from %s\n",inet_ntoa(client_addr.sin_addr));if(write(new_fd, hello, strlen(hello))==-1){fprintf(stderr,"Write Error:%s\n",strerror(errno));exit(1);}close(new_fd);}close(sockfd);exit(0);}Client:
#include <stdlib.h>#include <stdio.h>#include <errno.h>#include <string.h>#include <netdb.h>#include <sys/types.h>#include <netinet/in.h>#include <sys/socket.h>int main(int argc,char** argv){int sockfd;char buffer[1024];struct sockaddr_in server_addr;struct hostent *host;int portnumber,nbytes;if(argc!=3){fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);exit(1);}if((host = gethostbyname(argv[1]))==NULL){//获得访问的服务器的域名（如192.168.1.***）herror("Get host name error\n");exit(1);}if((portnumber = atoi(argv[2]))<0){fprintf(stderr,"Usage:%s hostname portnumber \a\n",argv[0]);exit(1);}//客户端建立sockfd描述符if((sockfd = socket(AF_INET,SOCK_STREAM,0))==-1){fprintf(stderr,"Socket Error %s\a\n",strerror(errno));exit(1);}//填充服务端的相关信息 主要是端口号，地址bzero(&server_addr,sizeof(server_addr));server_addr.sin_family = AF_INET;server_addr.sin_port = htons(portnumber);server_addr.sin_addr = *((struct in_addr *)host->h_addr);//客户端发起连接请求if(connect(sockfd, (struct sockaddr*)(&server_addr), sizeof(struct sockaddr))==-1){fprintf(stderr,"Connect Error:%s\a\n",strerror(errno));exit(1);}//如果连接成功if((nbytes = read(sockfd, buffer, 1024))==-1){fprintf(stderr,"Read Error:%s\n", strerror(errno));exit(1);}buffer[nbytes] = '\0';printf("Have Received : %s\n",buffer);close(sockfd);exit(0);}UDP
udpserver:
#include <stdlib.h>#include <stdio.h>#include <strings.h>#include <unistd.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#define PORT 2000 //监听端口#define MAXDATASIZE 100 //缓冲区大小int main(){int sockfd;struct sockaddr_in server;//服务器地址struct sockaddr_in client;//客户端地址int sin_size;int num;char msg[MAXDATASIZE];//接收缓冲区if((sockfd = socket(AF_INET, SOCK_DGRAM, 0))== -1){perror("Create socket failed.");exit(1);}bzero(&server,sizeof(server));server.sin_family = AF_INET;server.sin_port = htons(PORT);server.sin_addr.s_addr = htonl(INADDR_ANY);if(bind(sockfd, (struct sockaddr*)&server, sizeof(struct sockaddr)) == -1){perror("Bind error.");exit(1);}sin_size = sizeof(struct sockaddr_in);while(1){num = recvfrom(sockfd, msg, MAXDATASIZE, 0,(struct sockaddr*)&client, &sin_size);if(num<0){perror("recvfrom error\n");exit(1);}msg[num] = '\0';printf("Got a message(%s) from %s\n",msg,inet_ntoa(client.sin_addr));sendto(sockfd, "Weclome to server.\n", 23, 0, (struct sockaddr *)&client, sin_size);if(!strcmp(msg,"quit")){printf("quit!\r\n");break;}close(sockfd);return 0;}}udbclient:
#include <stdlib.h>#include <stdio.h>#include <unistd.h>#include <string.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <netdb.h>#define PORT 2000#define MAXDATASIZE 100int main(int argc, char ** argv){int sockfd, numbytes;char buf[MAXDATASIZE];struct sockaddr_in server,reply;struct hostent *host;if(argc!=3){printf("Usage :%s <IP ADDress> <message>\n",argv[0]);exit(1);}if((host = gethostbyname(argv[1]))==NULL){printf("gethosetbyname error\n");exit(1);}if((sockfd = socket(AF_INET, SOCK_DGRAM, 0))==-1){printf("socket() error\n");exit(1);}bzero(&server,sizeof(server));server.sin_family = AF_INET;server.sin_port = htons(PORT);server.sin_addr = *((struct in_addr *)host->h_addr);//发送消息至服务器sendto(sockfd,argv[2],strlen(argv[2]),0,(struct sockaddr*)&server,sizeof(struct sockaddr));while(1){int len;//接受来自服务器的消息if((numbytes = recvfrom(sockfd,buf,MAXDATASIZE,0, (struct sockaddr*)&reply,&len))==-1){printf("recvfrom() error\n");exit(1);}if(len != sizeof(struct sockaddr) || memcmp((const void*)&server, (const void*)&reply, len)!=0){printf("Receive message from other server.\n");buf[numbytes] = '\0';printf("Server Message: %s\n",buf);break;}close(sockfd);return 0;}}
