Learn socket programming in C on the linux platform. Learn socket programming in C on the linux platform. Write socket servers and client programs in C. TCP/IP socket programming in C. Introduction to Sockets Programming in C using TCP/IP Professor. Socket TCP IP Host Application Socket TCP IP. upon signal delivery to program. Socket programming with winsock This is a quick guide/tutorial to learning socket programming in C language. /* Create a TCP socket */ #include<stdio.h. UDP socket programming in winsock; Raw socket programming on. . Programming->C/C++ Sockets Tutorial. When a socket is created, the program has to specify the address domain and. with a stream socket, the underlying TCP protocol will detect that a message was lost because it.Want to watch this again later? Sign in to add this video to a playlist. An example TCP socket program with expanation. LINUX SOCKET PART 11: TCP CLIENT-SERVER CODE SAMPLE. Menu. $ gcc -g udpserver.c -o udpserver. Run the program and let it run in the background. TCP/IP and RAW socket, more program examples. . http:// Socket Programming. TCP/IP Programming in C. Learning to Program in C (Part 01) - Duration. Networking and Socket programming tutorial in CNetworking and Socket programming tutorial in C. This article is for programmers with the following requirements: Before you start learning socket programming make sure you already have a certain basic knowledge to network such as understand what is IP address, TCP, UDP. Before we start our tutorial, keep in mind that the following tutorial only works for Linux OS environment. If you are using Windows, I have to apologize to you because Windows has its own socket programming and it is different from Linux even though the connection concept is the same. Well, first copy and paste the following code and run it on server and client, respectively. Both code can be run on the same computer. It is always easy to understand after getting the code work. Socket- server. c#include < sys/socket. Buff[1. 02. 5]. listenfd = socket(AF_INET, SOCK_STREAM, 0). Buff, '0', sizeof(send. Buff)). serv_addr. AF_INET. serv_addr. INADDR_ANY). serv_addr. Failed to listenn"). NULL ,NULL). strcpy(send. Buff, "Message from server"). Buff, strlen(send. Buff)). close(connfd). Socket- client. c#include < sys/socket. Buff[1. 02. 4]. struct sockaddr_in serv_addr. Buff, '0' ,sizeof(recv. Buff)). if((sockfd = socket(AF_INET, SOCK_STREAM, 0))< 0). Error : Could not create socket n"). AF_INET. serv_addr. Error : Connect Failed n"). Buff, sizeof(recv. Buff)- 1)) > 0). Buff[n] = 0. if(fputs(recv. Buff, stdout) == EOF). Error : Fputs error"). Read Error n"). }After debugging both source files, run Socket- server. Socket- client. Attention here, never mess up with the order of executing Socket- server. Socket- client. Socket- server must be executed first then execute Socket- client. Socket- server forever loop. It means, you need to open two terminals to run each of the outputs. When you execute Socket- cli, I guess you will get the following result: If you see the message above, congratulations, you have success with your first step to networking programming. Otherwise, do some checking on your development environment or try to run some simple code for instance hello world. Why both server and client on the same computer? The answer is the server and client both are software but not hardware. It means what is happening on the top is there are two different software executed. To be more precise, the server and client are two different processes with different jobs. If you are experienced with constructing a server you might find out that a server can be built on a home computer by installing a server OS. It is because server is a kind of software. Understand sockets. Imagine a socket as a seaport that allows a ship to unload and gather shipping, whereas socket is the place where a computer gathers and puts data into the internet. Configure Socket. Things that need to be initialized are listed as follows: Using TCP or UDPAdditional protocol. Permit the incoming IP address. Assign the port used. At the beginning, a socket function needs to be declared to get the socket descriptor. Domain. AF_UNIX - connect inside same machine AF_INET – connect with different machine. Type. SOCK_STREAM – TCP connection SOCK_DGRAM – UDP connection Protocol. Define here when there is any additional protocol. Otherwise, define it as 0. Next, decide which struct needs to be used based on what domain is used above. AF_UNIXAF_INETstruct sockaddr_un. Use struct sockaddr_un if you are using AF_UNIX on your domain. It is required to include < sys/un. Use struct sockaddr_in if you are using AF_INT on your domain. On this article, I will explain sockadd_in that showed on the code above. AF_INET; Define the domain usedserv_addr. INADDR_ANY); Permit any incoming IP address by declare INADDR_ANYserv_addr. Declare port 5. 00. Based on example above, server is using port 5. You can check it by following commandsudo netstat - ntlp. Then, you will see following list. Inside red bracket, you will found 0. Socket- server, it means port 5. On client side, serv_addr. The flow chart below shows the interaction between client and server. The flow chart might looks complicated but make sure you don’t lost your patient due to the following flow chart. Because every process on the flow chart is needed and it acts a very important roles on network connection. After all setup on struct sockaddr_in is done, declare bind function. As flow chart, bind function must be declared on both server and client. Put socket description retrieved on the topaddress. Put struct sockaddr_in into it as domain is AF_INET. If your domain is AF_UNIX, tried put struct sockaddr_un here. Put the length of the address. Server and client will start interact with each other after the bind function and it is the most important session. From what flow chart shows, listen, accept, connect, three function play a very important roles. Imagine that server looks like an ATM, and only one person can be used the ATM. So, what happen if there is 2 or more people come at one time? The answer is simple, lining up and wait the front people finished using with ATM. It is exactly same as what happening in server. Listen function acts as waiting room, asking the traffic wait on the waiting room. Accept function acts as person who asking the traffic waiting inside the waiting room to be ready for the meeting between server. Last, connect function acts as the person who want to carry out some work with server. Put socket description retrieved on the topbacklog. Define the maximum of awaiting requestaccept functionserver_socket. Put socket description retrieved on the topclient_address. Put null here if there is no any special request to specify address. Put null here if second parameter is nullreturn. Return information of client socket description. Use it for interact between client and server. Put socket description retrieved on the topaddress. Put the struct sockaddr defined on the topaddress_len. Put the length of the address. Finally, after the request accepted. What should server and client do is send and read data. It is the most simple part in whole of this article. That’s all. read functionsocket_description. Put server or client socket description depend on reading data from server or clientread buffer. Content of the data retrievedread buffer length. Length of the output stringwrite functionsocket_description. Put server or client socket description depend on sending data to server or clientwrite buffer. Data to be sendwrite buffer length. Length of the output string. Personal Comment. This article was publish on 2. I was still new to networking programming on this period. Maybe there is some point that I am not make clear enough, I have tried all of my best to present all my knowledge to this article. Hope you can get the good basic beginning over here. Thank you. Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages. The Linux socket and network TCP client- server C program example. NETWORK PROGRAMMINGLINUX SOCKET PART 1. TCP CLIENT- SERVER CODE SAMPLEMenu. Working program examples if any compiled. IPs, run on Linux Fedora 3 with several. The Fedora machine used for the. No. Stack Execute". SELinux set to default configuration. All the. Beware codes that expand more than. Example: Connecting. TCP client to a server, a client program. Well, let try the client. The following example shows. Header files needed to use the sockets API. File contains Macro, Data Type and *//* Structure definitions along with Function *//* prototypes. Buffer. Length is 1. Buffer. Length 1. Default host name of server system. Change it. to your default *//* server hostname or IP. If the user do not. IP will be. used as default*/#define SERVER "The_server_name_or_IP"/* Server's port number */#define SERVPORT 3. Pass in 1 parameter which is either the *//* address or host name of the server, or *//* set the server name in the #define SERVER .. Variable and structure definitions. Buffer. Length]; char server[2. This is a test string from client. The socket() function returns a socket *//* descriptor representing an endpoint. The statement also identifies that the *//* INET (Internet Protocol) address family *//* with the TCP transport (SOCK_STREAM) *//* will be used for this socket. AF_INET, SOCK_STREAM, 0)) < 0){perror("Client- socket() error"); exit(- 1); }elseprintf("Client- socket() OKn"); /*If the server hostname is supplied*/if(argc > 1){/*Use the supplied argument*/strcpy(server, argv[1]); printf("Connecting to the f***ing %s, port %d ..n", server. SERVPORT); }else/*Use the default server name or IP*/strcpy(server, SERVER); memset(& serveraddr, 0x. AF_INET; serveraddr. SERVPORT); if((serveraddr. INADDR_NONE){/* When passing the host name of the server as a *//* parameter to this program, use the gethostbyname() *//* function to retrieve the address of the host server. NULL){printf("HOST NOT FOUND - -> "); /* h_errno is usually defined *//* in netdb. This is a client program- -- n"); printf("Command usage: %s < server name or IP> n", argv[0]); close(sd); exit(- 1); }memcpy(& serveraddr. After the socket descriptor is received, the *//* connect() function is used to establish a *//* connection to the server. Client- connect() error"); close(sd); exit(- 1); }elseprintf("Connection established..n"); /* Send string to the server using *//* the write() function. Write() some string to the server. Sending some string to the f***ing %s..n", server); rc = write(sd, data, sizeof(data)); if(rc < 0){perror("Client- write() error"); rc = getsockopt(sd, SOL_SOCKET, SO_ERROR, & temp, & length); if(rc == 0){/* Print out the asynchronously received error. SO_ERROR was"); }close(sd); exit(- 1); }else{printf("Client- write() is OKn"); printf("String successfully sent lol!n"); printf("Waiting the %s to echo back..n", server); }totalcnt = 0; while(totalcnt < Buffer. Length){/* Wait for the server to echo the *//* string by using the read() function. Read data from the server. Buffer. Length- totalcnt); if(rc < 0){perror("Client- read() error"); close(sd); exit(- 1); }else if (rc == 0){printf("Server program has issued a close()n"); close(sd); exit(- 1); }elsetotalcnt += rc; }printf("Client- read() is OKn"); printf("Echoed data from the f***ing server: %sn", buffer); /* When the data has been read, close() *//* the socket descriptor. Close socket descriptor from client side. Compile and. link the client program.[bodo@bakawali. Run the program. Before that don’t forget to run the server program first. The first. IP.[bodo@bakawali. Client- socket() OKHOST NOT FOUND - -> h_errno = 1- -- This is a client program- -- Command usage: ./tcpclient < server name or IP> [bodo@bakawali. Then run with. the server hostname or IP.[bodo@bakawali. Client- socket() OKConnecting to the f***ing 2. Connection established.. Sending some string to the f***ing 2. Client- write() is OKString successfully sent lol! Waiting the 2. 03. Client- read() is OKEchoed data from the f***ing server: This is a test string. And at the. server console messages.[bodo@bakawali. Server- socket() is OKServer- setsockopt() is OKUsing 0. Server- bind() is OKServer- Ready for client connection.. Server- accept() is OKServer- new socket, sd. OK.. Got connection from the f***ing client: 2. Server- read() is OKReceived data from the f***ing client: This is a test string. Server- Echoing back to client..[bodo@bakawali. UDP connectionless client/server. The connectionless protocol. APIs that are written for. User Datagram Protocol (UDP). The server and client examples use the. The following figure illustrates. APIs for a connectionless protocol. Figure 1: UDP connectionless APIs relationship. Connecting a UDP server and. The following examples show. UDP to connect a server to a connectionless client, and a connectionless. Example: Connecting a UDP. The first example shows. UDP to connect a connectionless server socket program to a client./*******************udpserver. Header files needed to use the sockets API. File contain Macro, Data Type and Structure *//* definitions along with Function prototypes. Server's port number, listen at 3. SERVPORT 3. 33. 3/* Run the server without argument */int main(int argc, char *argv[]){/* Variable and structure definitions. The socket() function returns a socket *//* descriptor representing an endpoint. The statement also identifies that the *//* INET (Internet Protocol) address family *//* with the UDP transport (SOCK_DGRAM) will *//* be used for this socket. AF_INET, SOCK_DGRAM, 0)) < 0){perror("UDP server - socket() error"); exit(- 1); }elseprintf("UDP server - socket() is OKn"); printf("UDP server - try to bind..n"); /* After the socket descriptor is received, *//* a bind() is done to assign a unique name *//* to the socket. In this example, the user *//* set the s_addr to zero. This allows the *//* system to connect to any client that uses *//* port 3. AF_INET; serveraddr. SERVPORT); serveraddr. INADDR_ANY); if((rc = bind(sd, (struct sockaddr *)& serveraddr, serveraddrlen)). UDP server - bind() error"); close(sd); /* If something wrong with socket(), just exit lol */exit(- 1); }elseprintf("UDP server - bind() is OKn"); printf("Using IP %s and port %dn", inet_ntoa(serveraddr. SERVPORT); printf("UDP server - Listening..n"); /* Use the recvfrom() function to receive the *//* data. The recvfrom() function waits *//* indefinitely for data to arrive. This example does not use flags that control *//* the reception of the data. Wait on client requests. UDP Server - recvfrom() error"); close(sd); exit(- 1); }elseprintf("UDP Server - recvfrom() is OK..n"); printf("UDP Server received the following: n "%s" messagen". Send a reply by using the sendto() function. In this example, the system echoes the received *//* data back to the client. This example does not use flags that control *//* the transmission of the data *//************************************************//* Send a reply, just echo the request */printf("UDP Server replying to the stupid UDP client..n"); rc = sendto(sd, bufptr, buflen, 0, (struct sockaddr *)& clientaddr. UDP server - sendto() error"); close(sd); exit(- 1); }elseprintf("UDP Server - sendto() is OK..n"); /* When the data has been sent, close() the *//* socket descriptor. Compile and. link the udp server program.[bodo@bakawali. Run the program and let. UDP server - socket() is OKUDP server - try to bind.. UDP server - bind() is OKUsing IP 0. UDP server - Listening..[1]+ Stopped. Verify the program running.[bodo@bakawali. S 1. 2: 2. 2. 0: 0. S+ 1. 2: 2. 4. 0: 0. Verify that the udp server. Without the. client program (next example) you can try telneting the server using port. For this program example the following telnet session. UDP/connectionless.[bodo@bakawali. Trying 2. 03. 1. 06. Connection refusedtelnet: Unable to connect to remote host: Connection refused. Example: Connecting a UDP. The following example shows. UDP to connect a connectionless client socket program to a server. This program will be used to connect to the previous UDP server./****************udpclient. Header files needed to use the sockets API. File contain Macro, Data Type and Structure *//* definitions along with Function prototypes. Host name of my system, change accordingly *//* Put the server hostname that run the UDP server program. This will be used as default UDP server for client connection. SERVER "bakawali"/* Server's port number */#define SERVPORT 3. Pass in 1 argument (argv[1]) which is either the *//* address or host name of the server, or *//* set the server name in the #define SERVER above. Variable and structure definitions. NULL */memcpy(buffer, "Hello! A client request message lol!", 3. The socket() function returns a socket *//* descriptor representing an endpoint. The statement also identifies that the *//* INET (Internet Protocol) address family *//* with the UDP transport (SOCK_DGRAM) will *//* be used for this socket. AF_INET, SOCK_DGRAM, 0)) < 0){perror("UDP Client - socket() error"); /* Just exit lol! UDP Client - socket() is OK!n"); /* If the hostname/IP of the server is supplied *//* Or if(argc = 2) */if(argc > 1)strcpy(server, argv[1]); else{/*Use default hostname or IP*/printf("UDP Client - Usage %s < Server hostname or IP> n". UDP Client - Using default hostname/IP!n"); strcpy(server, SERVER); }memset(& serveraddr, 0x. AF_INET; serveraddr. SERVPORT); if((serveraddr. INADDR_NONE){/* Use the gethostbyname() function to retrieve *//* the address of the host server if the system *//* passed the host name of the server as a parameter. NULL){printf("HOST NOT FOUND - -> "); /* h_errno is usually defined *//* in netdb. UDP Client - gethostname() of the server is OK.. Connected to UDP server %s on port %d.n", server. SERVPORT); }memcpy(& serveraddr. Use the sendto() function to send the data *//* to the server.
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