篇四 tcp,udp客户端服务器编程模型
一 前言
本篇内容主要介绍tcp，udp客户端服务器编程的基础API和示例代码。
二 API
三 ubuntu下代码示例
- TCP server
#include #include #include #include #include #include #include #include #define SA struct sockaddrint main(int argc,const char *argv[]){int sockfd = socket(AF_INET,SOCK_STREAM,0); //AF_INET IPV4；SOCK_STREAM TCP SOCK_DGRAM UDPif (sockfd < 0){perror(\"fail to socket\");exit(1);}struct sockaddr_in my_addr,peer_addr;bzero(&my_addr,sizeof(my_addr));my_addr.sin_family = AF_INET;my_addr.sin_port = htons(8080);//转换字节序my_addr.sin_addr.s_addr = inet_addr(\"0.0.0.0\");//inet_addr 把 IP 地址字符串转为整数;0.0.0.0表示绑定所有可用本地 IP，包括本地回环ip:127.0.0.1int ret_bind = bind(sockfd,(SA*)&my_addr,sizeof(my_addr));//绑定socket和本机ip，portif (ret_bind < 0){perror(\"fail to bind\");exit(1);}char buf[128];socklen_t len = sizeof(peer_addr);listen(sockfd,5); //将绑定端口后的socket改为监听状态，准备接收客户端连接请求，5表示等待建立连接的队列的长度，并不是服务器所连客户端数目int ret_recv;while(1){int confd = accept(sockfd,(SA*)&peer_addr,&len); //调用后，如果 accept() 成功，peer_addr 中会被内核写入发起连接的客户端的 IP 地址和端口号if (confd < 0){perror(\"fail to accept\");exit(1);}printf(\"ip:%s,port:%d is connect\\n\",inet_ntoa(peer_addr.sin_addr),ntohs(peer_addr.sin_port));while(1){bzero(buf,sizeof(buf));ret_recv = recv(confd,buf,sizeof(buf),0);if (ret_recv < 0){perror(\"fail to recv\");//perror可以打印系统调用错误信息，括号内为打印字头close(confd);break;}else if (ret_recv == 0){printf(\"peer is shutdown\\n\");close(confd);break;}else{printf(\"%s\\n\",buf);send(confd,buf,ret_recv,0);}}}return 0;}注：1.在上面这些接口里面，只有accept和recv是阻塞的，其他立即返回accept: 阻塞等待客户端连接，直到有连接请求到达才返回recv: 阻塞等待接收数据，直到有数据可读或连接关闭2.可用telnet 127.0.0.1 8080来测试（1）telnet是一个远程登录与测试通信的命令行工具，基于tcp协议，不能用来测试udp（2）相当于创建一个tcp client 去连接服务器 127.0.0.1 的8080端口，实现命令行交互- TCP client
#include #include /* See NOTES */#include #include #include #include #include #include #include #define SA struct sockaddrint main(int argc,const char* argv[]){ if (argc != 3) { printf(\"please input ip,port\\n\"); exit(1); } int sockfd = socket(AF_INET,SOCK_STREAM,0);//创建一个套接字 if (sockfd < 0) { perror(\"fail to socket\\n\"); exit(1); } struct sockaddr_in my_addr,peer_addr; bzero(&my_addr,sizeof(my_addr)); my_addr.sin_family = AF_INET; my_addr.sin_port = htons(6000); my_addr.sin_addr.s_addr = inet_addr(\"0.0.0.0\"); int ret_bind = bind(sockfd,(SA*)&my_addr,sizeof(my_addr));//将套接字和本机ip,port绑定 if(ret_bind < 0) { perror(\"fail to bind\\n\"); close(sockfd); exit(1); } char buf[128]; socklen_t len = sizeof(peer_addr); bzero(&peer_addr,sizeof(peer_addr)); peer_addr.sin_family = AF_INET; peer_addr.sin_port = htons(atoi(argv[2])); peer_addr.sin_addr.s_addr = inet_addr(argv[1]); int ret_connect = connect(sockfd,(SA*)&peer_addr,len);//connect 连接服务器 if (ret_connect < 0) { perror(\"fail to connect\\n\"); close(sockfd); exit(1); } while(1) { bzero(buf,sizeof(buf)); fgets(buf,sizeof(buf),stdin); send(sockfd,buf,strlen(buf),0); bzero(buf,sizeof(buf)); recv(sockfd,buf,sizeof(buf),0); printf(\"%s\\n\",buf); } return 0;}- UDP server
#include #include /* See NOTES */#include #include #include #include #include #include #include #define SA struct sockaddrint main(int argc,const char*argv){ int sockfd = socket(AF_INET,SOCK_DGRAM,0); if (sockfd < 0) { perror(\"fail to socket\\n\"); exit(1); } struct sockaddr_in my_addr,peer_addr; socklen_t len=sizeof(peer_addr); bzero(&my_addr,sizeof(my_addr)); my_addr.sin_family = AF_INET; my_addr.sin_port = htons(8080); my_addr.sin_addr.s_addr = inet_addr(\"0.0.0.0\"); int ret_bind = bind(sockfd,(SA*)&my_addr,sizeof(my_addr)); if (ret_bind < 0) { perror(\"fail to bind\\n\"); close(sockfd); exit(1); } char buf[128]; while(1) { bzero(buf,sizeof(buf)); bzero(&peer_addr,len); recvfrom(sockfd,buf,sizeof(buf),0,(struct sockaddr*)(&peer_addr),&len); //接收到数据时才知道对端信息 printf(\"ip:%s port:%d buf:%s \\n\",inet_ntoa(peer_addr.sin_addr),ntohs(peer_addr.sin_port),buf); sendto(sockfd,buf,strlen(buf),0,(struct sockaddr*)&peer_addr,len); } return 0;}//recvfrom,sendto和tcp recv，send是不一样的接口//nc 是一个强大的网络调试工具 nc -u 127.0.0.1 8080 可用来创建udp客户端来测试4.udp client
#include #include /* See NOTES */#include #include #include #include #include #include #include #define SA struct sockaddrint main(int argc,const char*argv[]){ if (argc != 3) { printf(\"please input ip and port\\n\"); return -1; } int sockfd = socket(AF_INET,SOCK_DGRAM,0); if (sockfd < 0) { perror(\"fail to socket\\n\"); exit(1); } struct sockaddr_in my_addr,peer_addr; bzero(&my_addr,sizeof(my_addr)); my_addr.sin_family = AF_INET; my_addr.sin_port = htons(6000); my_addr.sin_addr.s_addr = inet_addr(\"0.0.0.0\"); int ret_bind = bind(sockfd,(SA*)&my_addr,sizeof(my_addr)); if (ret_bind < 0) { perror(\"fail to bind\\n\"); close(sockfd); exit(1); } char buf[128]; bzero(&peer_addr,sizeof(peer_addr)); peer_addr.sin_family = AF_INET; peer_addr.sin_port = htons(atoi(argv[2])); peer_addr.sin_addr.s_addr = inet_addr(argv[1]); while(1) { bzero(buf,sizeof(buf)); fgets(buf,sizeof(buf),stdin); sendto(sockfd,buf,strlen(buf),0,(SA*)&peer_addr,sizeof(peer_addr)); bzero(buf,sizeof(buf)); recvfrom(sockfd,buf,sizeof(buf),0,NULL,NULL); printf(\"%s\\n\",buf); } return 0;}四 总结
1.tcp服务器和客户端编程，最关键的点其实是各调用了哪些API，及API调用顺序，其他都是细枝末节
2.udp相对简单些，API调用较少，但是要注意和tcp调用上的差别，参数，接口不全一样
